Automotive Engine Management (Mechatronics) PDF

KOFORIDUA TECHNICAL UNIVERSITY FACULTY OF ENGINEERING MECHATRONICS ENGINEERING DEPARTMENT COURSE TITLE AUTOMOTIVE ENGINE MANAGEMENT COURSE CODE AUM...

KOFORIDUA TECHNICAL UNIVERSITY FACULTY OF ENGINEERING MECHATRONICS ENGINEERING DEPARTMENT COURSE TITLE AUTOMOTIVE ENGINE MANAGEMENT COURSE CODE AUM 458 LECTURE NOTE BY: MR. JAMES OTENG, MPhil MECH.ENG  INTRODUCTION TO ENGINE MANAGEMENT An engine management system is a series of sensors, actuators, and a computer that work together to intelligently control the operation of your engine. The system's primary job is to decide how much fuel vapor to add to the engine cylinders at any given time, but the system does more than that. These systems also adjust the timing of ignition within the engine with careful precision. The ignition timing is adjusted to create smooth operating power that maintains perfect time even when driving at high speeds. An engine management system can be represented by the standard three-stage model as shown in Figure 1.1. 2 Figure 1.1 Representation of complete engine control as the standard functional system 3  SENSOR Engine sensors are used to observe the performance of the engine. Some of the sensors play a crucial role in the efficient output of an engine. The main function of engine sensors is to calculate the working condition and transfers the actual information to the computerized engine system. There are different types of Engine Sensors which are used for different types of operations. They are as follows: Thermocouple Sensor Oxygen Sensor Throttle Sensor Manifold Absolute Pressure Sensor Engine Speed Sensor Spark Knock Sensor 4  Manifold Absolute Pressure Sensor The manifold absolute pressure sensor (MAP sensor) is a crucial component in an internal combustion engine’s electronic control system. It’s commonly found in fuel-injected engines. The MAP sensor provides real-time information about the pressure inside the intake manifold to the engine’s electronic control unit (ECU). See Figure 1.2 5  Knock Sensor The spark knock sensor, also known as a knock sensor or knock detector, is a crucial component in modern internal combustion engines. Its primary function is to detect and mitigate engine knocking or detonation, which can lead to engine damage and reduced performance. Figure 1.3 6  Throttle Sensor This vital sensor allows your engine to maintain a proper amount of air. This feature is dependent on the throttle valve. When you press down on the gas pedal, your throttle body unit’s valve opens. This causes your throttle position sensor to adjust the engine intake manifold accordingly. This little sensor is essential to a correct mixture of air and fuel. It’s integrated with your engine control module and helps keep your idling and acceleration smooth. Figure 1.4 7 Oxygen Sensor An oxygen sensor is one type of sensor and it is available in the exhaust system of an automobile. The size and shape of this sensor look like a spark plug. Based on its arrangement in regard to the catalytic converter, this sensor can be arranged before (upstream) or after (downstream) the converter. Most of the automobiles which are designed after 1990 include upstream & downstream o2 sensors. Figure 1.5 8  Engine Speed Sensor The Society of Automotive Engineers (SAE) defines a speed sensor as a device that measures the number of revolutions or distance traveled per unit of time. The sensor typically either reads steel teeth moving past the sensor as the wheel spins or magnetic pulses from a series of small, carefully spaced magnets embedded in the bearing seal. The input shaft speed sensor tracks the speed of the input shaft, while the output shaft speed sensor detects the speed of the transmission output shaft. Figure 1.6 9 Crankshaft/Camshaft Position Sensors Engine timing relies on a perfect symphony between the crankshaft and camshaft – and their respective position sensors let the ECM know precisely where each one is at. If those positions don’t line up to what they should be, you need to know as soon as possible 10  Air Temperature The air temperature coming into the engine is a critical part of maximizing engine performance. That’s why the intake air temperature sensor (IAT) tells the ECM the air temperature, so it makes adjustments and maximizes performance. 11  Coolant Temperature Sensor Another critical sensor in your engine is the coolant temperature sensor. This sensor monitors your coolant temperature, which is a great way to determine your engine’s overall temperature. If it gets too hot, engine damage can occur. 12  Engine Oil Level Sensor One of the most common sensors in your vehicle is the engine oil level sensor. This sensor measures the oil level in your engine oil pan to ensure that it’s at a safe operating capacity. If you don’t have enough oil, this sensor will cause an oil level warning light on your dashboard. 13  ELECTRONIC CONTROL UNIT An electronic control unit (ECU), or electronic control module (ECM), is a common electronic device or module. Although it can be used in various fields such as medical, communications, and industrial control, the most discussed and recognized application is in the automotive industry. In terms of physical appearance, an ECU typically takes the form of a square or rectangular box with multiple slots for connecting various input and output circuits. It captures vehicle information from sensors and processes data based on preset programs. It then sends commands to actuating mechanisms to achieve precise control. Figure 1.5 show an ECU. ECUs are typically designed to operate with 12V or 24V battery supply and work within a voltage range of 6V to 40V. They are also capable of functioning in a temperature range from -40°C to 120°C. Furthermore, ECUs are built to withstand vibrations up to 1000Hz, making them highly reliable and capable of functioning even under harsh driving conditions. 14  ECUs are equipped with advanced features like fault diagnostics, self-protection mechanisms, and active learning. For instance, if a sudden malfunction occurs during operation, the ECU’s built-in RAM records the fault situation and takes protective measures. It uses the driver programs stored in the RAM to allow the engine to continue running instead of an immediate shutdown. Figure 1.7show an ECU 15  ECU WORKING PRINCIPLE When a car is started, the ECU enters its working state. Most of the data is first collected by sensors or other input devices and stored in the ECU’s RAM. The CPU then retrieves and processes this data from RAM according to its instructions and programs. In some cases, the ECU may need to compare the actual data captured by sensors with reference data stored in ROM. These data are usually preconfigured constants, calibration values, or standards used for comparison or as benchmarks. Ultimately, the CPU’s built-in programs and algorithms are used to compare and calculate the data and output instructions to control the operation of actuators. In this process, if the sensor transmits digital signals, they go directly through the I/O interface. If it’s an analog signal, it needs to be converted to a digital signal through an A/D converter. 16  ACTUATORS An actuator can work as a mechanical or electro-mechanical tool transforming energy, usually in the form of electricity, hydraulics, or pneumatics, into regulated motion or force. The actuator is a crucial component in various mechanical systems that helps convert energy into motion. It is responsible for controlling and moving mechanisms or systems, enabling them to perform specific tasks or functions. There are different types of actuators, each designed for specific purposes and operating principles. Some common types include Electric actuators, Pneumatic actuators, Hydraulic actuators. 17 General block diagram of an ignition and fuel control system Figure 1.8 General block diagram of an ignition and fuel control system 18  Diagnostics Techniques LOGIC Diagnostics or fault finding is a fundamental part of an automotive technician’s work. The subject of diagnostics does not relate to individual areas of the vehicle. If your knowledge of a vehicle system is at a suitable level, then you will use the same logical process for diagnosing the fault, whatever the system. INFORMATION Information and data relating to vehicles are available for carrying out many forms of diagnostic work. The data may come as a book, online or on CD/DVD. This information is vital and will ensure that you find the fault – particularly if you have developed the diagnostic skills to go with it. The general type of information available is as follows: ✓ engine diagnostics, testing and tuning; ✓ servicing, repairs and times; ✓ fuel and ignition systems; ✓ auto electrics data; ✓ component location; ✓ body repairs, tracking and tyres. 19  WHERE TO STOP? This is one of the most difficult skills to learn. It is also one of the most important. The secret is twofold: know your own limitations – it is not possible to be good at everything; leave systems alone where you could cause more damage or even injury – for example, air bag circuits. Often with the best of intentions, a person new to diagnostics will not only fail to find the fault but also introduce more faults into the system in the process. I would suggest you learn your own strengths and weaknesses; you may be confident and good at dealing with mechanical system problems but less so when electronics is involved. Of course you may be just the opposite of this. Remember that diagnostic skill is in two parts – the knowledge of the system and the ability to apply diagnostics. If you do not yet fully understand a system, leave it alone until you do. 20  DIAGNOSTICS PROCESS The Six Stages of diagnostics 1. Verify: Is there actually a problem, can you confirm the symptoms 2. Collect: Get further information about the problem, by observation and research 3. Evaluate: Stop and think about the evidence 4. Test: Carry out further tests in a logical sequence 5. Rectify: Fix the problem 6. Check: Make sure all systems now work correctly 21 ADVANCE ELECTRONIC DIAGNOSTICS ON- BOARD DIAGNOSTICS 22  INTRODUCTION TO ON- BOARD DIAGNOSTICS On-Board Diagnostics (OBD) is an automotive term referring to a vehicle's self-diagnostic and reporting capability. OBD systems give the vehicle owner or repair technician access to the status of the various vehicle sub-systems. The amount of diagnostic information available via OBD has varied widely since its introduction in the early 1980s versions of on-board vehicle computers. Early versions of OBD would simply illuminate a malfunction indicator light or "idiot light" if a problem was detected but would not provide any information as to the nature of the problem. Modern OBD implementations use a standardized digital communications port to provide real-time data in addition to a standardized series of diagnostic trouble codes, or DTCs, which allow a person to rapidly identify and remedy malfunctions within the vehicle. The current versions are OBD2 and European OBD2 (EOBD2). The standard OBD2 and EOBD2 are quite similar. Types of On-Board Diagnostics (OBD) OBD-I The regulatory intent of OBD-I was to encourage auto manufacturers to design reliable emission control systems that remain effective for the vehicle's "useful life". The hope was that by forcing annual emissions testing for California, and denying registration to vehicles that did not pass, drivers would tend to purchase vehicles that would more reliably pass the test. OBD-I was largely unsuccessful, as the means of reporting emissions-specific diagnostic information was not standardized 23. Technical difficulties with obtaining standardized and reliable emissions information from all vehicles led to an inability to implement the annual testing program effectively. The Diagnostic Trouble Codes (DTC's) of OBD-I vehicles can usually be found without an expensive 'scan tool'. Each manufacturer used their own Diagnostic Link Connector (DLC), DLC location, DTC definitions, and procedure to read the DTC's from the vehicle. DTC's from OBD-I cars are often read through the blinking patterns of the 'Check Engine Light' (CEL) or 'Service Engine Soon' (SES) light. By connecting certain pins of the diagnostic connector, the 'Check Engine' light will blink out a two-digit number that corresponds to a specific error condition. The DTC's of some OBD-I cars are interpreted in different ways, however. Cadillac (gasoline) fuel-injected vehicles are equipped with actual on-board diagnostics, providing trouble codes, actuator tests and sensor data through the new digital Electronic Climate Control display. Holding down 'Off' and 'Warmer' for several seconds activates the diagnostic mode without the need for an external scan tool. Some Honda engine computers are equipped with LEDs that light up in a specific pattern to indicate the DTC. General Motors, some 1989-1995 Ford vehicles (DCL), and some 1989-1995 Toyota/Lexus vehicles have a live sensor data stream available; however, many other OBD-I equipped vehicles do not. OBD-I vehicles have fewer DTC's available than for OBD-II equipped vehicles. 24  OBD 1.5 OBD 1.5 refers to a partial implementation of OBD-II which General Motors used on some vehicles in 1994, 1995, & 1996. (GM did not use the term OBD 1.5 in the documentation for these vehicles — they simply have an OBD and an OBD-II section in the service manual.) For example, the 94–95 Corvettes have one post- catalyst oxygen sensor (although they have two catalytic converters), and have a subset of the OBD-II codes implemented. OBD-II OBD-II is an improvement over OBD-I in both capability and standardization. The OBD-II standard specifies the type of diagnostic connector and its pinout, the electrical signaling protocols available, and the messaging format. It also provides a candidate list of vehicle parameters to monitor along with how to encode the data for each. There is a pin in the connector that provides power for the scan tool from the vehicle battery, which eliminates the need to connect a scan tool to a power source separately. However, some technicians might still connect the scan tool to an auxiliary power source to protect data in the unusual event that a vehicle experiences a loss of electrical power due to a malfunction. Finally, the OBD-II standard provides an extensible list of DTCs. As a result of this standardization, a 25 single device can query the on-board computer(s) in any vehicle. OBD SCANNERS 26  This OBD-II came in two models OBD-IIA and OBD-IIB. OBD-II standardization was prompted by emissions requirements, and though only emission-related codes and data are required to be transmitted through it, most manufacturers have made the OBD-II Data Link Connector the only one in the vehicle through which all systems are diagnosed and programmed. Note: The best OBD Diagnostic tools may include; Innova carscan pro 5210, Ancel BD310 Autel Autolink Al539, ThinkOBD100, JethaxOBD2Scanner, TopdonArtlink500, SeekOne SK860 etc. OBD Scanners OBD scanners are devices that let you read and diagnose error codes a vehicle displays. Without them, it will be difficult to locate faults with vehicles. In most cases mechanics use these devices to diagnose car problems. Currently, there are two different types of OBD Scanners; OBD II code readers OBD II Scan tools 27 Various tools are available that plug into the OBD connector to access OBD functions. These range from simple generic consumer level tools to highly sophisticated OEM dealership tools to vehicle telematics devices. Some examples of these devices are; 1. Hand-held scan tools Multi-brand vehicle diagnostics system handheld Autoboss V-30 with adapters for connectors of several vehicle manufacturers. A range of rugged hand-held scan tools is available. Simple fault code readers/reset tools are mostly aimed at the consumer level. Professional hand-held scan tools may possess more advanced functions I. Access more advanced diagnostics II. Set manufacturer- or vehicle-specific ECU parameters III. Access and control other control units, such as air bag or ABS IV. Real-time monitoring or graphing of engine parameters to facilitate diagnosis or tuning 28 2. Mobile device-based tools and analysis Mobile device applications allow mobile devices such as cell phones and tablets to display and manipulate the OBD-II data accessed via USB adaptor cables or Bluetooth adapters plugged into the car's OBD II connector. PC-based scan tools and analysis platforms. https://upload.wikimedia.org/wikipedia/commons/thumb/7/79/Obd_usb_kkl_interface.jpg/220px-Obd_usb_kkl_interface.jpg Typical simple USB KKL Diagnostic Interface without protocol logic for signal level adjustment. A PC-based OBD analysis tool that converts the OBD-II signals to serial data (USB or serial port) standard to PCs or Macs. The software then decodes the received data to a visual display. Many popular interfaces are based on the ELM or STN1110 OBD Interpreter ICs, both of which read all five generic OBD-II protocols. Some adapters now use the J2534 API allowing them to access OBD-II Protocols for both cars and trucks. 29 In addition to the functions of a hand-held scan tool, the PC-based tools generally offer: Large storage capacity for data logging and other functions Higher resolution screen than handheld tools The ability to use multiple software programs adding flexibility The identification and clearance of fault code Data shown by intuitive graphs and charts The extent that a PC tool may access manufacturer or vehicle-specific ECU diagnostics varies between software products as it does between hand-held scanners. https://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Texa_obd-log.png/220px-Texa_obd-log.png 3. Data loggers 30 TEXA OBD log. Small data logger with the possibility to read out the data later on PC via USB. Data loggers are designed to capture vehicle data while the vehicle is in normal operation, for later analysis. Data logging uses include: Engine and vehicle monitoring under normal operation, for the purposes of diagnosis or tuning. Some US auto insurance companies offer reduced premiums if OBD-II vehicle data loggers or cameras are installed - and if the driver's behavior meets requirements. This is a form of auto insurance risk selection Monitoring of driver behavior by fleet vehicle operators. Analysis of vehicle black box data may be performed on a periodic basis, automatically transmitted wirelessly to a third party or retrieved for forensic analysis after an event such as an accident, traffic infringement or mechanical fault. Emission testing Since OBD-II stores trouble codes for emissions equipment, the testing computer can query the vehicle's onboard computer and verify there are no emission related trouble codes and that the vehicle is in compliance with emission standards for the model year it was manufactured. 31  4. The OBD II connector (Serial port communications) Most modern vehicle systems now have ECUs that contain self-diagnosis circuits. The information produced is read via a serial link using a scanner. A special interface, stipulated by one of a number of standards is required to read the data. The standards are designed to work with a single- or two-wire port allowing many vehicle electronic systems to be connected to a central diagnostic plug. The sequence of events to extract DTCs from the ECU is as follows: 1. Test unit transmits a code word. 2. ECU responds by transmitting a baud rate recognition word. 3. Test unit adopts the appropriate setting. 4. ECU transmits fault codes. 32 The test unit converts the DTCs to suitable output text. Further functions are possible, which may include the following: Identification of ECU and system to ensure the test data is appropriate to the system currently under investigation. Read out of current live values from sensors. Spurious figures can be easily recognised. Information such as engine speed, temperature, air flow and so on can be displayed and checked against the test data. System function stimulation to allow actuators to be tested by moving them and watching for suitable response. Programming of system changes such as basic idle CO or changes in basic timing can be programmed into the system. 33  4. The OBD II connector (Serial port communications) https://upload.wikimedia.org/wikipedia/commons/thumb/8/85/OBD_002.jpg/270px-OBD_002.jpg Female OBD-II connector on a car The OBD2 connector lets you access data from your car easily. The standard SAE J1962 specifies two female OBD2 16-pin connector types (A & B). A few things to note: The OBD2 connector is near your steering wheel, but may be hidden behind covers/panels Not all male connectors fit all OBD2 female sockets - check the type and OBD port pin-outs Pin 16 supplies power via the car battery - often also while the ignition is off 34  Pins 6 (CAN-H) and 14 (CAN-L) are most relevant as CAN (ISO 15765-4) is standard in most modern cars (incl. EVs) https://upload.wikimedia.org/wikipedia/commons/thumb/c/c7/OBD_connector_shape.svg/220px-OBD_connector_shape.svg.png Female OBD-II connector pinouts - front view The OBD-II specification provides for a standardized hardware interface—the female 16-pin (2x8) J1962 connector. Unlike the OBD-I connector, which was sometimes found under the hood of the vehicle, the OBD-II connector is required to be within 2 feet (0.61 m) of the steering wheel (unless an exemption is applied for by the manufacturer, in which case it is still somewhere within reach of the driver). 5. Driver's supplementary vehicle instrumentation Driver's supplementary vehicle instrumentation is instrumentation installed in a vehicle in addition to that provided by the vehicle manufacturer and intended for display to the driver during normal operation. This is opposed to scanners used primarily for active fault diagnosis, tuning, or hidden data logging. 35 Auto enthusiasts have traditionally installed additional gauges such as manifold vacuum, battery current etc. The OBD standard interface has enabled a new generation of enthusiast instrumentation accessing the full range of vehicle data used for diagnostics, and derived data such as instantaneous fuel economy. Instrumentation may take the form of dedicated trip computers capture or interfaces to PDAs, smartphones, or a Garmin navigation unit. As a capture is essentially a PC, the same software could be loaded as for PC-based scan tools and vice versa, so the distinction is only in the reason for use of the software. These enthusiast systems may also include some functionality similar to the other scan tools. Vehicle telematics OBD II information is commonly used by vehicle telematics devices that perform fleet tracking, monitor fuel efficiency, prevent unsafe driving, as well as for remote diagnostics and by Pay-As-You-Drive insurance. Although originally not intended for the above purposes, commonly supported OBD II data such as vehicle speed, RPM, and fuel level allow GPS-based fleet tracking devices to monitor vehicle idling times, speeding, and over-revving. By monitoring OBD II DTCs a company can know immediately if one of its vehicles has an engine problem and by interpreting the code the nature of the problem. OBD II is also monitored to block mobile phones when driving and to record trip data for insurance purposes. 36  VEHICLE IDENTIFICATION NUMBER The vast majority of new cars have their VINs located under the front of the windshield and typically visible through a small, clear square within the tinted area. Depending on the year and price of the car you're looking at, what's there will vary: It could be a nicely stamped piece of aluminum, or it could be a cheap plastic tag. Both are usually riveted onto the dash in order to make replacement difficult. Limited-edition models or expensive sports cars may also have a special VIN plate located in the door sill or on the dash. Figure 1.7 shows a VIN 37 BREAKDOWN OF A VIN 38  As you can see in the graphic above, the VIN is composed of six parts: Make/Model: (Digits 1-3) this breaks out the vehicle's make, model, and manufacturer. Vehicle Features: (Digits 4-8) these digits identify the various features of the specific model — trim specifications, driveline options, etc. Verifying #: (Digit 9) Determined through a complex mathematical formula that relates to the other numbers in the VIN; used to verify that the VIN itself is not fake. Model Year: (Digit 10) represents the vehicle's model year, which is not to be confused with the year it was sold or delivered. Assembly Plant: (Digit 11) an internal digit that shows where the car was built. Sequence of Model Production: (Digit 12-17) these digits indicate the order in which the vehicle left the assembly line. This is effectively the serial number. 39  The Society of Automotive Engineers (SAE) assigns the WMI (world manufacturer identifier) to countries and manufacturers. The following list shows a small selection of world manufacturer WMI Manufacturer codes. AAV (South Africa) Volkswagen AFA (South Africa) Ford CL9 (Tunisia) Wallyscar JA (Japan) Isuzu JF (Japan) Fuji Heavy Industries JH (Japan) Honda JMB (Japan) Mitsubishi JMZ (Japan) Mazda JN (Japan) Nissan JS (Japan) Suzuki JT (Japan) Toyota KL (South Korea) Daewoo/GM Korea KMH (South Korea) Hyundai KN (South Korea) Kia KPT (South Korea) SsangYong LVZ (China) DFSK NMT (Turkey) Toyota SAJ (United Kingdom) Jaguar SAL (United Kingdom) Land Rover 40 SAR (United Kingdom) Rover SB1 (United Kingdom) Toyota SCC (United Kingdom) Lotus Cars SCE (United Kingdom) DeLorean SHH (United Kingdom) Honda SJN (United Kingdom) Nissan Micro Compact Car AG (SMART 1998- TCC (Switzerland) 1999) TMA (Czech Republic) Hyundai TMB (Czech Republic) Škoda TRU (Hungary) Audi 41 TSM (Hungary) Suzuki U5Y (Slovakia) Kia UU (Romania) Dacia VA0 (Austria) ÖAF VF1 (France) Renault VF3 (France) Peugeot VF6 (France) Renault Trucks/Volvo VF7 (France) Citroën VFE (France) IvecoBus VNK (France) Toyota VSS (Spain) SEAT VV9 (Spain) Tauro Sport Auto WAU (Germany) Audi WAP (Germany) Alpina WBA (Germany) BMW WBS (Germany) BMW M 42 43  As shown above, the 10th character of the VIN indicates its model year. A: 1980 or 2010 B: 1981 or 2011 C: 1982 or 2012 D: 1983 or 2013 E: 1984 or 2014 F: 1985 or 2015 G: 1986 or 2016 H: 1987 or 2017 J: 1988 44  K: 1989 L: 1990 M: 1991 N: 1992 P: 1993 R: 1994 S: 1995 T: 1996 V: 1997 W: 1998 X: 1999 Y: 2000 45 ON BOARD DIAGNOSTICSII CODES 46  ON BOARD DIAGNOSTICSII CODES How to Interpret Car Diagnostic Codes The car diagnostic codes, AKA Diagnostic Trouble Codes, consists of a five-digit alphanumeric code. The formats are shown below: 47 OBD provides monitoring for various systems. They include the engine control module, body, chassis, etc. When you look at an OBD II code, you can immediately tell where the fault is by reading the letters and numbers it contains. Below is a breakdown. The First Character (Letter) All OBDII codes start with a letter that denotes the part of the vehicle that has a fault. Let’s check it out, shall we? P – Powertrain. It includes the engine, transmission, and all the associated accessories. U – Network & Vehicle Integration. These are functions that are managed and shared by on board computer systems. B – Body. These are parts mainly found in the passenger compartment area. C – Chassis. It covers mechanical systems and functions like steering, suspension, and braking. 48 The Second Character (Number) A number usually follows the first letter. This number can only be ‘0’, ‘1’, ‘2’, or ‘3’. 0 – If it’s a ‘0’, ‘2’, or ‘3’, then the code is a standardized (SAE) code; also known as generic code 1 – If it’s a ‘1’ then you’re looking at a manufacturer-specific code The Third Character (Number/Letter) This number denotes the particular vehicle system that has a fault. There are eight systems in total: 0–Fuel and air metering and auxiliary emission controls 1–Fuel and air metering 2–Fuel and air metering (injector circuit) 3–Ignition systems or misfires 4–Auxiliary emission controls 5–Vehicle speed control and idle control systems 6–Computer and output circuit 7 – Transmission A-F – Hybrid Trouble Codes The Fourth and Fifth Characters (Number) The final piece of a DTC is a two-digit number. This number defines the exact problem that you’re dealing with. It can be any number between 0 and 99. 49 As you can see, a typical DTC has five characters in total, and each one of those characters gives it a description. For example, if you get the code P0219, it means that the car has an engine over-speed condition. The ‘P’ means that the problem is in the powertrain. The ‘0’ means that it’s a generic code while the ‘2’ refers to the fuel and air metering (injector circuit) system. The last two digits (19) define the problem; i.e., an over-speed condition. As mentioned already, DTC codes that start with ‘P’ relate to the powertrain. Those that begin with ‘U’ are for the network and vehicle integration system. The letter ‘B’ refers to the vehicle’s body while ‘C’ is for the chassis. Below are some examples of OBD codes; a) P0010 Intake Camshaft Position Actuator Circuit / Open (Bank The P0010 code happens when the ‘bank 1’ camshaft and the crankshaft have a variation in mechanical timing. The problem occurs when the engine experiences high RPM. The ECM doesn’t correctly adjust valve lift at high RPM. Main Symptoms: Check Engine Light comes on Engine performs poorly at high RPM 50 Car runs roughly  Lower fuel economy Car fails emission test Possible Causes: Sludge in engine oil Faulty OVC (oil control valve) Internal damage to ECM ECM timing is out of sync Wiring damage Malfunction of crankshaft or camshaft sensor A short in VCT/VVT circuit, or the circuit is open Diagnostic Steps: Use an advanced diagnostic tool to pull engine codes Inspect the VVT/VCT solenoid system for dirty oil Inspect the circuit for wiring problems b) P0011 Intake Camshaft Position Timing – Over-Advanced (Bank 1) The P0011 code is triggered when the camshaft timing for bank 1 is above the limit set by the ECM. This situation causes an over-advanced condition that occurs either during retarding or advancing the camshaft timing. 51 Main Symptoms: Check Engine Light comes on Hard starting Poor idle Car may run rough or stall Poor fuel economy Car may fail emission test Possible Causes: Camshaft remains advanced despite ECM commanding it to retard Bank 1 oil control solenoid may be clogged or stuck Oil may be too thick and is thus blocking passages in bank 1 Wiring problems in VCT/VVT Oil continuously flows to VCT piston chambers open Diagnostic Steps: Check that engine oil is clean and has the recommended viscosity Visually inspect wiring in the CVT system Pull engine codes and live data using advanced diagnostic tool C. P0012 Intake Camshaft Position Timing – Over-Retarded (Bank 1) The P0012 code is triggered when bank 1 is having an over-retarded timing condition that occurs either during retarding or advancing. 52 Main Symptoms: Check Engine Light comes on Hard starting Poor fuel economy Car may run rough or stall Car may fail emission test Possible Causes: Camshaft timing is incorrect Wiring problems in VCT/VVT Oil continuously flows to VCT piston chamber Timing valve solenoid control has failed and is stuck in open position Oil may be too thick and is thus blocking passages in bank 1 Diagnostic Steps: Check that engine oil is clean Visually inspect wiring in the CVT system Pull engine codes and live data using advanced diagnostic tool Using bidirectional scanner, command the timing valve solenoid control valve to open and close then see if camshaft timings change. If they change it means the valve is not the problem 53 D. P0014 Exhaust Camshaft Position Timing – Over-Advanced (Bank 1) The P0014 code happens when bank 1 camshaft is having an over-advanced timing condition that occurs either during retarding or advancing. Main Symptoms: Check Engine Light comes on Hard starting Poor fuel economy Car may run rough or stall Car may fail emission test Possible Causes: Camshaft timing is incorrect Wiring problems in VCT/VVT Oil continuously flows to VCT piston chamber Timing valve solenoid control has failed and is stuck in open position Oil may be too thick and is thus blocking passages in bank 1 Diagnostic Steps: Check that engine oil is clean and full in the tank Visually inspect wiring in the CVT system 54 Pull engine codes and live data using advanced diagnostic tool  Using bidirectional scanner, command the timing valve solenoid control valve to open and close then see if camshaft timings change. If they change it means the valve is not the problem E. P0016 Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A The P0016 code occurs when the crankshaft and camshaft signals are out of time. Meaning the ECM can detect that the timing of the crankshaft and that of the camshaft do not correlate Main Symptoms: Check Engine Light comes on Engine may crank but fail to start Engine may continue to run but will record poor performance Rattling sound in the harmonic balancer Poor fuel economy Possible Causes: Timing chain is overstretched Tone ring on camshaft and/or crankshaft is has slipped or broken Timing chain has jumped teeth and put camshaft timing out of position Problems with camshaft phase and putting the phaser out of position Wiring to crank/cam sensor is damaged 55 Diagnostic Steps: Inspect oil control valve (OCV) for connection or wiring problems Check that engine oil is clean, full and has correct viscosity Pull engine codes and live data using advanced diagnostic tool Using bidirectional scanner, command the OVC on and off then see if camshaft timings change. If they change it means the valve is not the problem F. P0037 Heated Oxygen Sensor (H02S) Heater Control Circuit Bank 1 Sensor 2 The P0037 code is triggered when bank 1, sensor 2 of the O2 sensor heater circuit is faulty. For example, the engine isn’t achieving closed loop and causes the car to increase emissions. Main Symptoms: Check Engine Light comes on Longer time needed to achieve closed loop Decreased fuel economy Engine may go into fixed fuel mix 56 Possible Causes: H02S sensor in bank 1, circuit 2 is not sending the correct signal to ECM Damaged or failed element in the heater circuit Open in O2 sensor heater’s circuit Open/short in O2 sensor heater’s battery Defective ECM (this is the least likely cause) Diagnostic Steps: Inspect wiring and power to the O2 sensor and ensure there’s no damage/open/short Use code reader to pull engine codes Check voltage of O2 sensor and ensure it matches manufacturer’s specs Replace O2 sensor if necessary G. P0102 Mass or Volume Air Flow Circuit low Input The P0102 code happens when the mass airflow (MAF) sensor is not performing within the standard expectation and is therefore sending a lower signal than usual (due to low voltage). 57 Main Symptoms: Check Engine Light comes on Extremely low fuel consumption and thus internal engine problems Engine runs roughly Car idles and stalls frequently Possible Causes: Defective MAF sensor Presence of dirt and debris in MAF (restricts airflow) Leaks in air intake system Improper wiring of the circuit to MAF sensor Diagnostic Steps: Use code reader to pull engine codes Visually inspect MAF sensor wiring and circuit Check for air leaks in air intake system Inspect MAF to see if there’s dirt and debris 58 H. P0106 Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem The P0106 code is triggered when the Powertrain Control Module (PCM) has not detected a change in engine speed, throttle angle, and exhaust gas recirculation (EGR) despite an increase in manifold absolute pressure (MAP). An increase in MAP indicates an increase in engine load. Main Symptoms: Check Engine Light comes on Poor fuel economy Engine fails to idle Engine produces black smoke (visible at tailpipe) Erratic acceleration Possible Causes: Faulty MAP sensor Air intake component is loose, cracked or doesn’t have its plastic fitting Water or dirt affecting connector to MAP sensor Corrosion may be causing poor signal to and from MAP sensor PCM is defective (least likely but not unlikely) 59 Diagnostic Steps: Use an advanced scanner to pull engine codes. With that scanner, diagnose the MAP sensor when the engine is off, and the key is on. It should be similar or close to barometric pressure (BARO) reading. Start the engine and see if MAP sensor readings drop significantly. If they do, the sensor is working correctly. I. P0113 Intake Air Temperature Circuit High Input (Sensor 1) P0113 means that the signal voltage from the intake air temperature (IAT) is above 5V, which is more than the expected range. Main Symptoms: Check Engine Light comes on Engine may run extra lean Possible Causes: Defective IAT sensor Loose or faulty wiring at IAT sensor Open or short in IAT ground circuit, signal circuit or reference circuit PCM is defective (least likely but not unlikely) 60 Diagnostic Steps: Use an advanced scanner to pull engine codes. View live data from the IAT sensor. If the result is less than -30 degrees Celsius, then the sensor is likely to be faulty. Otherwise, it’s probably an intermittent problem. Check the wiring for opens and loose connections. J. P0118 Engine Coolant Temperature Circuit High Input P0118 means that the PCM has determined that ECT is less than freezing temp yet the engine has been running for several minutes, which shouldn’t happen. Main Symptoms: Check Engine Light comes on Poor fuel economy Engine fails to idle and may not start completely Engine produces black smoke (visible at tailpipe) Possible Causes: Defective ECT sensor Open or short in ECT signal or ground circuit PCM is defective (least likely but not unlikely) 61 Diagnostic Steps: Using an OBD2 scanner, check the ECT. If it’s a logical reading, the problem is intermittent. Perform a wiggle test while looking out for drop-outs. If there are any, there’s a bad connection to or from the ECT sensor. K. P0121 Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem P0121 happens when the PCM has detected that the throttle position sensor (TPS) voltage is more or less than it should be for the current RPM. Main Symptoms: Check Engine Light comes on Car produces black smoke (visible at tailpipe) Car stumbles when you accelerate or decelerate Engine may fail to start completely Possible Causes: Defective TPS Open or short in TPS circuit Loose or bad connection to TPS PCM is defective (least likely but not unlikely) 62 Diagnostic Steps: Visually inspect all wiring to TPS for loose, open, or short connections Using an OBD2 scanner, check for live data and freeze-frame data from TPS. If it doesn’t read 0.5 at idle and 4.5 at full throttle, the TPS is faulty L. P0122 Throttle/Pedal Position Sensor/Switch a Circuit Low Input P0122 means that the PCM is reporting that the TPS has recorded a voltage that is lower than the minimum limit. The value varies from one car to another, but the code may come when the voltage hits 0.20V or less. Main Symptoms: Check Engine Light comes on Extremely high idle Rough or low idle Car stalls Acceleration is low or completely lacking 63 Possible Causes: Defective TPS Open or short in TPS circuit Improper mounting of TPS after replacement TPS has loosened PCM is defective (least likely but not unlikely) Diagnostic Steps: Visually inspect all wiring to TPS for loose, open, or poor connections. Check that TPS is tightly in position, especially if you recently replaced it. M. P0128 Coolant Thermostat (Coolant Temperature below Thermostat Regulating Temperature) P0128 OBD2 code means the PCM has detected that the engine has not attained the required temperature despite it is on for enough time to reach that temperature. Main Symptoms: Check Engine Light MAY come on Engine temp drops when the vehicle is in high speed Engine takes abnormally long to warm 64 Possible Causes: Most likely cause is that thermostat is leaking or stuck in open position Engine coolant level is too low Defective IAT sensor Defective ECT sensor Defective cooling fan Diagnostic Steps: Check whether coolant strength and level are in the recommended range Check whether IAT sensor, ECT sensor and coolant fan are working If all the above are okay then the thermostat is the problem N. P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1) P0131 triggers when the ECM has determined that there’s a low voltage condition in bank 1 sensor 1; i.e. O2 sensor voltage remained too low for longer than 2 minutes. 65 Main Symptoms: Check Engine Light comes on Car produces black smoke (visible at tailpipe) Poor fuel economy Engine may fail to start completely If it starts it may run rough and/or stumble Possible Causes: Mostly a problem related to corrosion, loose terminal or burnt wire in the O2 sensor 1 connector Defective O2 sensor Open or short in wiring to O2 sensor O2 circuit is experiencing high resistance Diagnostic Steps: Visually inspect all wiring to O2 sensor 1 for loose, open or short connections Use a wiggle test to determine where the voltage drops out Using an OBD2 scanner, check whether sensor 1 of bank 1 is switching properly O. P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1) P0133 occurs when the O2 sensor or ECM can’t adjust air to fuel ratio as it’s supposed to even when the engine is running. 66 Main Symptoms: Generally doesn’t come with symptoms. However, in some cases the Check Engine Light may come on and fuel economy may reduce Possible Causes: First O2 sensor in bank 1 is faulty Short, open or broken wire in O2 sensor circuit Exhaust leak Diagnostic Steps: Visually inspect all wiring to first O2 sensor for loose, open or short connections Use a wiggle test to determine where the voltage drops out Visually check for exhaust leaks or air inlet leaks Using an OBD2 scanner, check whether sensor 1 of bank 1 is switching properly P). P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) Usually, when O2 heater attains operating temperature, O2 sensor switches based on ambient temp. If ECM determines that the O2 sensor took too long to switch this code is set. It applies to the first sensor of bank 1 Main Symptoms: Check Engine Light comes on Poor fuel economy 67 Possible Causes: Short, open or broken wire in O2 heating system High resistance in O2 heater element or circuit Diagnostic Steps: Visually inspect all wiring to first O2 sensor (bank 1) for loose, open or short connections Use a wiggle test to determine where the voltage drops out If the code is persistent replace O2 sensor Q. P0136 O2 Sensor Circuit Malfunction (Bank 1 Sensor 2) P0136 means that the ECM has determined that the there’s a low voltage condition in bank 1 sensor 2; i.e. O2 sensor voltage remained too low for longer than 2 minutes. Main Symptoms: Check Engine Light comes on Car produces black smoke (visible at tailpipe) Poor fuel economy Engine may fail to start completely If it starts it may run rough and/or stumble 68 Possible Causes: Mostly a problem related to corrosion, loose terminal or burnt wire in the O2 sensor 2 connector Defective O2 sensor Open or short in wiring to O2 sensor O2 circuit is experiencing high resistance Diagnostic Steps: Visually inspect all wiring to O2 sensor 2 for loose, open or short connections Use a wiggle test to determine where the voltage drops out Using an OBD2 scanner, check whether sensor 2 of bank 1 is switching properly R). P0137 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2) Basically same as P0136. The P0137 is triggered when the PCM has detected that the O2 sensor may be inactive. Main Symptoms: Generally doesn’t come with symptoms. However, in some cases the Check Engine Light may come on and fuel economy may reduce Possible Causes: Faulty O2 sensor Short, open or broken wire in O2 sensor circuit Defective heater circuit in O2 sensor High resistance in O2 heater element or circuit 69  Faulty fuel pump regulator resulting in very high or very low fuel pressure Exhaust leak Diagnostic Steps: Visually inspect all wiring to O2 sensor for loose, open or short connections Use a wiggle test to determine where the voltage drops out Visually check for exhaust leaks or air inlet leaks If the code is persistent replace O2 sensor S. P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2) The P0138 code means heated O2 sensor in bank 1 sensor 2 is giving a higher voltage reading than it should. For most vehicles the code comes when voltage exceeds 1.5V. Main Symptoms: Generally doesn’t come with symptoms. However, in some cases the Check Engine Light may come on and fuel economy may reduce Possible Causes: Fuel temp is excessively high Short, open or broken wire in O2 sensor circuit 70 Diagnostic Steps: Visually inspect all wiring to O2 sensor for loose, open or short connections Use a wiggle test to determine where the voltage drops out Using an OBD2 scanner, check whether sensor 1 of bank 2 is switching properly T. P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) P0141 means when O2 heater attains operating temperature, O2 sensor switches based on ambient temp. If ECM determines that the O2 sensor took too long to switch this code is set. It applies to the second sensor of bank 1. Main Symptoms: Check Engine Light comes on Poor fuel economy Possible Causes: Short, open or broken wire in O2 heating system High resistance in O2 heater element or circuit Diagnostic Steps: Visually inspect all wiring to second O2 sensor (bank 1) for loose, open or short connections Use a wiggle test to determine where the voltage drops out If the code is persistent replace O2 sensor 71 U. P0161 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2) P0161 triggers when O2 heater attains operating temperature, O2 sensor switches based on ambient temp. If ECM determines that the O2 sensor took too long to switch this code is set. It applies to the second sensor of bank 2. Main Symptoms: Check Engine Light comes on Poor fuel economy Possible Causes: Short, open or broken wire in O2 heating system High resistance in O2 heater element or circuit Diagnostic Steps: Visually inspect all wiring to second O2 sensor (bank 2) for loose, open or short connections Use a wiggle test to determine where the voltage drops out If the code is persistent replace O2 sensor V. P0171 System Too Lean (Bank 1) P0171 indicates that there is a lean condition in bank 1; i.e. there’s excess oxygen in the exhaust 72 Main Symptoms: Significant decrease in engine power Car hesitates then surges upon acceleration Rough idle Possible Causes: Dirty or defective MAF sensor MAF sensor has a vacuum leak Positive Crankcase Ventilation (PCV) valve is stuck in open position Leak either in PCV or vacuum system Diagnostic Steps: Inspect MAF sensor in bank 1 for dirt and debris Check whether fuel pressure is correct Check vacuum and PCV for leaks Run a smog test using OBD2 scanner W. P0172 System Too Rich (Bank 1) P0172 happens when there’s a rich condition in bank 1; i.e. there’s too little oxygen in the exhaust condition in bank 1; i.e. there’s excess oxygen in the exhaust. 73 Main Symptoms: Generally doesn’t come with symptoms but the Check Engine Light may come on and engine may misfire Possible Causes: Dirty or defective MAF sensor MAF sensor has a vacuum leak Problem relating to fuel pressure or delivery Diagnostic Steps: Inspect MAF sensor in bank 1 for dirt and debris Check whether fuel pressure is correct Inspect fuel lines and injectors for any leaks/openings and dirt Check vacuum, PCV and exhaust for leaks Run a smog test using OBD2 scanner X. P0174 System Too Lean (Bank 2) This code means that there’s a lean condition in bank 2; i.e. there’s excess oxygen in the exhaust 74 Main Symptoms: Significant decrease in engine power Car hesitates then surges upon acceleration Rough idle Possible Causes: Dirty or defective MAF sensor MAF sensor has a vacuum leak Positive Crankcase Ventilation (PCV) valve is stuck in open position Leak either in PCV or vacuum system Diagnostic Steps: Inspect MAF sensor in bank 2 for dirt and debris Check whether fuel pressure is correct Check vacuum and PCV for leaks Run a smog test using OBD2 scanner 75 Y. P0300 Random/Multiple Cylinder Misfire Detected When the code P0300 is triggered, it means that PCM has detected that there’s an engine cylinder that’s not firing properly. It could be one or more cylinders. PCM hasn’t specified the exact cylinder Main Symptoms: Check Engine Light comes on Check Engine Light may flash Engine lacks power Engine may be hard to start Engine may stumble and hesitate frequently Possible Causes: Defective or worn out spark plugs Low fuel pressure.Vacuum leak Defective catalytic converter Defective fuel injector Defective coil Bad camshaft position sensor Defective crankshaft sensor Problem with distributor 76 Diagnostic Steps: Using a scan tool, pull codes and see if there are any other besides P0300. Address the others first Inspect whether there are loose, open or short wires in ignition coils Inspect whether spark plugs and their wires are in good condition Check that fuel pressure is within the recommended range Inspect fuel injectors to see whether they are in good condition Z. P0301 Cylinder 1 Misfire Detected The meaning of P0301 is that the PCM has detected that cylinder #1 is not firing properly. Main Symptoms: Check Engine Light comes on Check Engine Light may flash Engine lacks power Engine may be hard to start Engine may stumble and hesitate frequently Possible Causes: Defective or worn out spark plugs in cylinder 1 Low fuel pressure 77  Vacuum leak Defective catalytic converter Defective fuel injector Defective coil Defective camshaft position sensor Defective crankshaft sensor Problem with distributor Diagnostic Steps: Using a scan tool, pull codes and see if there are any other besides P0301. Address the others first Inspect whether there are loose, open or short wires in ignition coils in cylinder 1 Inspect whether cylinder 1 spark plugs and their wires are in good condition Check that fuel pressure is within the recommended range Inspect fuel injectors to see whether they are in good condition 78 DIAGNOSING OBD II TROUBLESHOOTING CODES IN MOTOR VEHICLE USING A MOBILE DEVICE- BASED TOOL 79  DIAGNOSING OBD II TROUBLESHOOTING CODES IN MOTOR VEHICLE USING A MOBILE DEVICE-BASED TOOL: Step 1: Locate your vehicle’s OBD port The OBD-II port is usually located under the dashboard, beneath the steering wheel column (1-3 in the diagram below). If not located beneath the steering wheel column, look for the port in the areas indicated by numbers 4-9. 80 Step 2: Plug your OBD-II scan tool into the connector Step 3: Pair your OBD-II Scanner with an App 81 Download a DTC code scanning App, and turn on Bluetooth to pair with the OBD-II Scanner. When the scanner is paired with your phone, the App will show the diagnostic results. Use the ZUS App as an example, after creating your vehicle profile and pairing the OBD-II Scanner, you can do the following to get an overview of your vehicle: Safety Center & Engine Health Scan Decode & Clean Error Codes Pro Dashboard & Driving Habits Analysis Car Finder & Mileage With this information, you can get a great overview of your vehicle’s condition, your driving habits, your travel record, and use it to find your car when you forgot where you parked. 82 DIAGNOSING OBD II TROUBLESHOOTING CODES IN MOTOR VEHICLE USING A LAPTOP AS AN AUTOMOTIVE SCAN TOOL. Modern automobiles come equipped with an On-board Diagnostics system. OBD-II is an advanced management system that professionals and home mechanics can connect to via the diagnostic port. You can also use a computer or laptop instead of a handheld scanner, however, you will need a kit. Most laptop diagnostic software is more advanced than handheld scanners, offering the ability to monitor engine performance, as well as read trouble codes. Step 1 Purchase a laptop OBD-II interface kit. You can purchase these kits at many automotive parts stores; in addition, they are available online. Step 2 Insert the software installation disc. Follow the prompts to complete the installation. If the installation does not automatically begin, access "My Computer" and double-click on the disc to start. Step 3 Connect the components to your laptop. Most kits contain a USB to serial adapter for laptops without serial ports. Once the device is attached to the laptop, connect the OBD-II diagnostic port cable. 83 Step 4 Start the software program. Double-click on the desktop icon if the program did not automatically start. Get comfortable with the control interface. Step 5 Bring your laptop to your vehicle. Turn the ignition key to the "On" position, but do not crank the engine. Connect the OBD-II scan cable from the laptop to the diagnostic port on your vehicle, usually located in the driver's side foot well, below the steering well. Click the "Scan" button on the control interface, if required. View the engine codes and diagnostic information provided by the program. OBD II AND I/M PROGRAMS OBD II systems monitor and report on the condition of vehicle emissions control systems. As such OBD II system interrogation has a place in, and should be a benefit to, a modern light-duty vehicle emissions Inspection and Maintenance (I/M) program. 84 OBD II AND I/M PROGRAMS OBD II systems monitor and report on the condition of vehicle emissions control systems. As such OBD II system interrogation has a place in, and should be a benefit to, a modern light-duty vehicle emissions Inspection and Maintenance (I/M) program. However, I/M administrators should be aware that OBD II interrogation in an I/M program represents a major change in vehicle emission control system evaluation and monitoring. The tailpipe emission tests that have been employed in I/M programs for decades provide a 'snap- shot' of emissions at the time of the test whereas OBD II interrogation provides a report from a system that monitors emission control system performance on a near continuous basis. In addition, OBD II systems identify deteriorated components or systems that, if allowed to further deteriorate, will result in higher emissions. One OBD II system goal is to identify components in need of repair before emission standards are exceeded. Although there is some controversy in regard to specifics, by their nature OBD II interrogations have a place in I/M programs. In the USA, EPA regulations require states to include OBD system checks within the so-called 'enhanced' I/M programs and both the EPA and CARB have provided guidance on how to perform such tests. In regard to the vehicles to be included in the OBD II interrogation portion of an I/M program, in the USA the EPA requires all 1996 MY and newer vehicles be included in the OBD inspection. In Canada, LDVs were not required to be OBD II compliant until the 1998. 85 Issues Regarding OBD II Tests in I/M Programs Although OBD II checks are now required to be included in I/M program in the USA, there are concerns related to those checks or tests. The OBD Workgroup reviewed the most recent information on three areas of concern raised in the July, 2001 National Research Council (NRC)/National Academy of Sciences (NAS) report, Evaluating Vehicle Emissions Inspection and Maintenance Programs. These concerns were related to the: Effectiveness of 'pollution prevention' approach of OBD. That is the difference between an OBD II interrogation and a tailpipe emissions test; The detection of a lack of overlap in some vehicles that fail the traditional tailpipe test and vehicles that fail OBD checks; and OBD failure criteria and potentially high failure rates for aging vehicles equipped with OBDII (1996 and newer vehicles). Other concerns in regard to OBD II testing in I/M programs include the physical application of the OBD II test, including the operation of the Malfunction Indicator Lamp (MIL) and the interpretation of the Readiness Monitor codes. Another issue in regard to the use of OBD II in I/M programs concerns possible difficulties in evaluating OBD II test program effectiveness. 86 OBD II - The Identification of High and Low Emissions The results from some studies have shown that OBD II systems may either fail to detect vehicles with emissions well in excess of standards, errors of omission, or activate DTCs for vehicles with emissions that are below standards, errors of commission. High Emitters - Errors of Omission A number of vehicles have been uncovered which are above 1.5 x certification OBD trigger threshold as measured on the Federal Test Procedure. In all cases these vehicles should have been identified by the OBD II system as in need of repair and the MIL commanded 'on'. A consistent problem for tailpipe emission tests is the lack of adequate preconditioning. This is particularly true for the IM240 test where the IM 240 test may produce a false failure if preconditioning is insufficient. The I/M Administration found that some of the high emitting vehicles that were not detected by their OBD II systems were the result of manufacturer's OBD II design problems and these problems were being addressed by the manufacturers. The OBD II systems installed by some manufacturers have been found to be 'under-sensitive'. These under- sensitive OBD systems have failed to detect malfunctions at the proper levels More of the vehicles that had the MIL illuminated were found to be genuine high emitters and the total emission reductions achieved by successfully repairing these vehicles were greater than those achieved from the IM240 group. 87 While the ability of OBD II to identify high emitters must be monitored, there appears to be evidence to support its ability to capture high emitters. Anomalies in the OBD II systems produced by some manufacturers may account for some of the unidentified high emitters. Low Emitters - Errors of Commission The OBD II system is designed to identify malfunctioning emissions control components before emissions standards are exceeded. Therefore, OBD systems can identify deteriorated or broken components or systems that 'lead' to higher emissions. OBD systems identify repairs needed to prevent further deterioration of broken emission control components. The current specification for OBD II systems is that the MIL will illuminate if a problem is detected that results in, or could potentially result in, emissions higher than 1.5 times vehicle's emissions certification standard. Studies show that if OBD II were used to decide whether a vehicle passes or fails an I/M inspection, most OBD II failing vehicles would have emissions less than 1.5 times the standard. That is because the emission control system malfunction that the OBD II detects may not yet have resulted in increased emissions. Also many current I/M programs have much higher cut points than 1.5 times the vehicle’s certification standard. Therefore, since OBD II is designed to detect problems and not to measure emissions, it is not necessarily a sign of an OBD II system malfunction that an MIL light is illuminated on a vehicle whose emissions are within set standards. 88 Fault codes can be cleared from the ECU memory in two ways: 1. Using the facilities of a fault code reader (scanner) to clear the memory; 2. Disconnecting the battery earth lead for about two minutes (on some systems this does not work). The first method is clearly recommended because disconnecting the battery will also ‘reset’ many other functions such as the radio code, the clock and even the learnt or adaptive functions in the ECUs. 89 THANK YOU 90