Automotive Electricity and Electronics Level-III PDF

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Automotive Electricity and Electronics Suspension Systems Vehicle Maintenance Technology

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This document covers Automotive Electricity and Electronics Level-III material on Service and Repair Electronically Controlled Suspension Systems. It details different types of suspension systems and their components, including sensors, control units, and actuators, along with the technology employed.

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Automotive Electricity and Electronics Level -III Service and Repair Electronically Controlled Suspension Systems This module covers the units:  Understanding electronically controlled suspension system  Testing electronically controlled suspension system  Maintaining...

Automotive Electricity and Electronics Level -III Service and Repair Electronically Controlled Suspension Systems This module covers the units:  Understanding electronically controlled suspension system  Testing electronically controlled suspension system  Maintaining electronically controlled suspension systems Unit one Understanding electronic suspension system Basic requirement of vehicle suspension system As a vehicle moves, the suspension and tires must react to the current driving conditions. Specifically, the suspension system:  Supports the weight of the vehicle  Keeps the tires in contact with the road  Controls the direction of the vehicle’s travel  Attempts to maintain the correct vehicle ride height  Maintains proper wheel alignment  Reduces the effect of shock forces as the vehicle travels on an irregular surface Suspension System Types The two primary types of suspension systems are active and passive. Passive Suspension Systems: Shock absorbers and springs are examples of fixed mechanical components used in passive suspension systems. They offer a dependable and easy-to-use solution, but they don’t adapt to changing traffic patterns or road conditions. Active Suspension Systems: In contrast, active systems continuously and instantaneously adjust the suspension characteristics through the use of sensors and state-of-the-art technology. Because they are adjustable, active suspensions can provide an excellent balance between handling performance and ride comfort. CONT.. How Function Active Suspension Systems? Active suspension systems use a variety of sensors to track the movements of the automobile as well as outside variables including the road’s condition, the driver’s actions, and the speed of the vehicle. The central control unit receives real-time data from these sensors and modifies the suspension settings accordingly. The following are a few essential elements and procedures of suspension systems: CONT.. Sensors: These can include accelerometers, wheel speed sensors, height sensors, and other kinds of sensors. They are constantly collecting data regarding the vehicle’s movements and external factors. Control Unit: A centralized control unit makes fast decisions about how to adjust the suspension settings by analyzing sensor data. Actuators: Electric or hydraulic actuators are used to alter the suspension’s characteristics, such as the ride height or damping rates. Modifiable Algorithms: Adaptive algorithms are sophisticated algorithms that use sensor data, driver input, and preset performance criteria to establish the optimal suspension settings. These algorithms ensure that the suspension system responds effectively and quickly to changing conditions. CONT.. CONT.. the sum of the first control parameters corresponding to the differences between the actual vehicle heights detected and the associated desired vehicle heights and the second control parameters corresponding to the changing amounts of the vehicle height differences. The second control parameters are so set that the higher the vehicle speed is, the higher the second quantities are in magnitude, enhancing the controllability and stability of the vehicle under higher vehicle speed conditions and ensuring a greater comfort ability level of the vehicle under lower vehicle speed conditions. CONT.. Block diagram of hydraulic active suspension CONT.. Electromagnetically controlled active suspensions work similarly to hydraulically controlled systems. The only difference is that these systems use electromagnet motors instead of pumps to adjust a car’s ride height. This type of active electronic suspension is known to respond faster and use less power than hydraulics. Electromagnetic active suspension system CONT.. Each actuator maintains a sort of hydraulic equilibrium with the others to carry the vehicle’s weight, while maintaining the desired body attitude. At the same time, each actuator serves as its own shock absorber, eliminating the need for yet another traditional suspension component. In other words, each hydraulic actuator acts as both a spring (with variable-rate damping characteristics) and a variable-rate shock absorber. This is accomplished in an active suspension system by varying the hydraulic pressure within each cylinder and the rate at which it increases or decreases. By bleeding or adding hydraulic pressure from the individual actuators, each wheel can react independently to changing road conditions. The components that make such a system possible are the actuator control valves, various sensors, and the chassis computer. Feeding information to a computer are a number of specialized sensors. CONT.. Adaptive Suspensions o Adaptive suspensions use electronic shock absorbers with variable valve action. o In some cases, variable air spring rates are used to adapt the vehicle’s ride characteristics to the prevailing road conditions or driver demands. o Electronic sensors monitor factors such as vehicle height, vehicle speed, steering angle, braking force, door position, shock damping status, engine vacuum, throttle position, and ignition switching. o A computer is used to analyze this input and switch the suspension into a preset operating mode that matches existing conditions. Some systems are fully automatic. Others allow the driver to select the ride mode CONT.. System Components o Compressor o Sensors o Electronic Shock Absorbers o Electronic Struts o Computer Control Module o Electronic Leveling Control Operating principle of electronic suspension system  The basic idea behind simpler electronic suspensions is to use electronically adjustable shocks and/or struts so suspension ride control characteristics can be adjusted or adapted to changing driving conditions, resulting in improved ride and handling.  Electronic shocks and struts have a small electric actuator motor mounted either atop the unit or inside to rotate a control rod or selector valve that opens or closes metering orifices in the piston valve.  This changes the relative stiffness of the shock as it travels through compression and rebound. The next generation of electronic shocks will use solenoids rather than motors because solenoids allow faster response times. CONT..  The position of the control rod or selector valve inside the shock or strut is determined by a dash-mounted switch in manually controlled systems and/or a microprocessor in systems with more sophisticated automatic controls. Working Principles of Spring and damper systems  spring will move about its equilibrium position until it reaches rest state. The damper in this system is used to dissipate some of the energy released by the spring such that the number and amplitude of the oscillations brought by the spring are reduced. Electronic Damping Control Electronic damping control allows the selection of different amounts of damping according to the prevailing road conditions. The system monitors various input parameters (vehicle load, road condition and driving style) and selects the most appropriate damper setting. The result is optimum damping over the full range of road conditions and driving styles. Most manufacturers allow for at least three settings; ‘soft’, ‘medium’ and ‘firm’, and the most recent systems allow for continuously variable damper control. CONT.. Block diagram of electronic dampening control Selectable Ride (SR) The Selectable Ride (SR) system is the most basic of the electronic systems offered by General Motors. Selectable Ride (SR) allows the driver to choose between two distinct damping levels:  Firm  Normal SR is found on Chevrolet and GMC full-size pickup trucks. Selectable Ride as used on Chevrolet and GMC pickup trucks CONT.. o A switch is used to control four electronically controlled gas charged dampers. The mode select switch activates the bi-state (two settings) dampers at all four corners of the vehicle, allowing the driver to select vehicle ride characteristics. The system is either energizing or de-energizing the bi-state dampers to provide a firm or normal ride. Automatic Level Control The Automatic Level Control (ALC) system automatically adjusts the rear height of the vehicle in response to changes in vehicle loading and unloading. Automatic Level Control is found on many General Motors vehicles. ALC controls rear leveling by monitoring the rear suspension position sensor and energizing the compressor to raise the vehicle or energizing the exhaust valve to lower the vehicle. ALC has several variations across the different platforms. ALC maintains the same ride height either loaded or unloaded by increasing or decreasing the air pressure in the rear air shocks. Automatic level system Air Suspension (AS) Air Suspension (AS) is a system very similar to the ALC system. The purpose of the AS system includes: 1. Keep the vehicle visually level 2. Provide optimal headlight aiming 3. Maintain optimal ride height The AS system includes the following components: An air suspension compressor assembly Rear air springs Air suspension sensors Schematics of Air suspension components CONT..  The AS system is designed to maintain rear trim height within 3/16 inch (4 mm) in all loading conditions, and the leveling function will deactivate if the vehicle is overloaded. The AS system also includes an accessory air inflator found in the rear cargo area. Variable-Rate Air Springs In an air spring system with ordinary shock absorbers, the ECM uses the air springs to control trim height and is used on many Ford, Mercury, and Lincoln vehicles. The three height sensors transmit a signal to the ECM that reflects trim height at each axle. The ignition and brake light switches tell the ECM whether the ignition switch is on or off, and if the brake pedal is depressed. The dome light switch indicates whether any doors are open. The on/off switch disables the air spring system to avoid unexpected movement while towing or servicing the vehicle. CONT.. Variable - rate air springs  The typical variable-rate air spring system uses three height sensors, two in the front and one in the rear, to monitor trim height and to provide input signals to the ECM. CONT..  The ECM receives information from the height sensors indicating that the trim height is too high or too low, and it energizes the actuators to add or bleed air from the air springs. The system actuators can still operate for up to an hour after the ignition is switched off.  Any time the ignition is switched to the “run” position, the ECM raises the vehicle, if necessary, within the first 45 seconds. If trim height is too high and the vehicle must be lowered, the ECM delays doing so for 45 seconds after the ignition is switched on. An air compressor with a regenerative dryer provides the air change required to inflate the air springs on the air suspension system, and a vent solenoid is used to relieve air pressure and deflate the springs. CONT.. Air spring assembly  The air spring compressor assembly is usually mounted on rubber cushions to help isolate it from the body of the vehicle. All of the air entering or leaving the air springs flows through the regenerative air dryer. CONT..  By energizing the compressor relay, the ECM directs current to turn on the compressor motor when trim height needs to be raised. The ECM command to lower the vehicle is an electrical signal that opens the vent solenoid to bleed air pressure out of the system. Solenoid valve regulating air flow into the air spring Computer Command Ride o The Computer Command Ride (CCR) system controls ride firmness by automatically controlling an actuator in each of the four struts to increase ride firmness as speed increases. The three damping modes are: Comfort Normal Sport o Damping mode selection is controlled by the CCR control module according to vehicle speed conditions, driver select switch position, and any error conditions that may exist. In the perform ride mode, the system will place the damping level in the firm mode regardless of vehicle speed. In the touring ride mode, the damping level depends on vehicle speed Schematic showing Computer Command Ride (CCR) system Real-Time Dampening and Road-Sensing Suspension Real-time dampening (RTD) independently controls a solenoid in each of the four shock absorbers in order to control the vehicle ride characteristics and is capable of making changes within milliseconds (0.001 second). Road-sensing suspension (RSS), along with ALC, controls damping forces in the front struts and rear shock absorbers in response to various road and driving conditions. RTD and RSS incorporate the following components: An electronic suspension control module, Front and rear suspension position sensors, Bi-state dampers, A ride select switch, and An air compressor is used on some models CONT.. Schematic showing the shock control used in the RSS system Bi-State and Tri-State Dampers The bi-state damper is also known as a solenoid controlled damper. Bi-state dampers are found on the RTD, RSS, and SR systems. Each of the suspension dampers used in these systems have an integral solenoid. The solenoid valve provides various amounts of damping by directing hydraulic damping fluid in the suspension shock absorber or strut. CONT.. solenoid valve controlling shock absorber  The General Motors version of ESC is called the vehicle stability enhancement system (VSES) and includes an additional level of vehicle control to the EBCM. VSES is also known as Stabile track. The purpose of the vehicle stability enhancement system along with the antilock brake system (ABS) is to provide vehicle stability enhancement during over steer or under steer conditions.  The pulse-width modulation (PWM) voltage signal from the suspension control module controls the amount of current flow through each of the damper solenoids. With a low PWM signal de- energized, more hydraulic damping fluid is allowed to bypass the main suspension damper passage, resulting in a softer damping mode. As the PWM signal increases, or is energized, the damping mode becomes more firm. CONT.. The main difference between a tri-state damper and a bi-state damper is that the tri-state damper uses an electrical actuator, whereas the bi-state damper is solenoid controlled. The three damping modes include: Comfort Normal Sport A tri-state damper has an integral electrical strut actuator that rotates a selector valve to change the flow of hydraulic damping fluid. The CCR module controls the operation of the strut actuators to provide the three damping modes. The strut position input provides feedback to the CCR module. The strut position input is compared to the commanded actuator position to monitor system operation. CONT.. Dampening modes of a CCR shock absorber with integral shock solenoid Magneto-Rheological (MR) Suspension MR fluid shocks use a working fluid inside the shock that can change viscosity rapidly depending on electric current sent to an electromagnetic coil in each device. The fluid is called magneto rheological (MR) and is used in mono tube-type shock absorbers. This type of shock and suspension system is called the magneto rheological real-time damping (MRRTD) or chassis continuously variable real-time dampening magneto-rheological suspension (CCVRTMR). Under normal operating conditions, the fluid flows easily through orifices in the shock and provides little dampening. When a large or high-frequency bump is detected, a small electrical current is sent from the chassis controller to an electromagnetic coil in each shock and the iron particles in the fluid respond within 3 milliseconds (ms), aligning themselves in fiber like strands. CONT.. Vehicles that use magneto-rheological shock absorbers have a sensor located near each wheel, as shown on this C6 Corvette The controller for the magneto-rheological suspension system on a C6 Corvette is located behind the right front wheel. This causes the MR fluid to become thick like peanut butter and increases the firmness of the shock. This type of shock absorber is used to control squat during acceleration and brake dive as well as to reduce body roll during cornering by the chassis controller. CONT.. Magneto-rheological shock absorber Construction of Electronic Suspension System The major components of an electronic suspension system are illustrated in Figure above. The system may be considered in terms of three functional blocks. Electronic Controlled Suspension Sensors The sensors provide the control unit with the necessary information to allow the computer to recognize and evaluate a variety of driving styles, road conditions and vehicle loads. Figure 6 below illustrates the wide variety of sensor inputs that may be used. A. Height Sensors A height sensor senses the vertical relationship between the suspension component and the body. Its signal indicates to the ECM how high the frame or body is, or how compressed the suspension is. A number of sensor designs are use determine ride height, including a photocell type of sensor. Four height sensors, one at each wheel, deliver an input signal to the ECM. All four sensors are similar and use a control link, lever, slotted disc, and four photo interrupters to transmit a signal. Each photo interrupter consists of a light-emitting diode (LED) and a phototransistor, which reacts to the LED. CONT.. Inside the sensor, the LEDs and phototransistors are positioned opposite each other on each side of the slotted disc. When the system is activated, the ECM applies voltage to the LEDs, which causes them to illuminate. Light from an LED shining on the phototransistor causes the transistor to generate a voltage signal. Signals generated by the phototransistors are delivered to the ECM as an input that reflects ride height. CONT..  As suspension movement rotates the disc, the slots or windows on the disc either allow light from the LEDs to shine on the phototransistors or prevent it.  The windows are positioned in such a manner that, in combination with the four LEDs and transistors, the sensor is capable of generating 16 different levels of voltage.  This variable voltage, which is transmitted to the ECM as an input signal, directly corresponds to 1 of 16 possible positions of the suspension. This input signal tells the ECM the position of the suspension in relation to the body. Whether the input voltage signal is increasing or decreasing allows the ECM to determine if the suspension is compressing or extending.  The ECM can also determine the relative position of the body to the suspension, or the attitude of the vehicle, from the four height sensors. Comparing front-wheel input signals to those of the rear wheels determines the amount of pitch caused by forces of acceleration or deceleration. A side-to-side comparison allows the ECM to determine the amount of body roll generated by cornering force. B. Steering angle sensor Depending on the vehicle, the steering wheel position sensor may also be called a hand wheel position sensor. The function of this sensor is to provide the control module with signals relating to steering wheel position, the speed and direction of hand wheel position. The sensor is found on most real-time dampening (RTD) and road-sensing suspension (RSS) applications. The sensor is typically located at the base of the steering column. Always refer to service information for vehicle-specific information. Steering angle sensor location CONT..  The hand wheel sensor produces two digital signals, which are used by the electronic brake control module (EBCM). These signals are produced as the steering wheel is rotated.  The sensor can also produce more than two signals. As an example, the Cadillac Escalade hand wheel sensor produces one analog and three digital signals. The sensor uses a 5-volt signal reference. Analog signal voltage values increase or decrease, between 0 and 5 volts, as the steering wheel is moved left and right of center. The digital signal is also a standard power-to-ground circuit as shown in the schematic. There are three possible digital signals:  Phase A  Phase B  Index pulse CONT..  These signals provide the suspension control module with steering wheel speed and direction information. Digital signals are either high or low, 5 volts or 0 volts. A scan tool provides diagnostic trouble code (DTC) faults for this sensor. If there is an intermittent concern with a steering wheel position sensor, select the movie mode or snapshot features on a scan tool and slowly turn the steering wheel lock to lock. After the snapshot is complete, plot the analog sensor voltage to see if the signal dropped out. Any dropout is an indication of an intermittent problem. Steering angle sensor signals C. Lateral acceleration sensor The function of the lateral accelerometer sensor is to provide the suspension control module with feedback regarding vehicle cornering forces. This type of sensor is also called a G-sensor, with the letter “G” representing the force of gravity. Lateral acceleration sensor What does a Yaw Rate Sensor do? A Yaw Rate Sensor (or rotational speed sensor) measures a vehicle's angular velocity about its vertical axis in degrees or radians per second in order to determine the orientation of the vehicle as it hard-corners or threatens to roll-over. CONT.. How does a Yaw Rate Sensor function? In simpler terms, the yaw rate sensor is a key component in a vehicle’s stability control or electronic stability control system. Yaw can be defined as the movement of an object turning on its vertical axis. The yaw rate sensor determines how far off-axis a car is "tilting" in a turn using gyroscopes to monitor the slip angle, the angle between the vehicle’s heading and actual movement direction. This information is then fed into the vehicle’s computer to evaluate the wheel speed, steering angle and accelerator position, and, if the system senses too much yaw, the appropriate braking force is automatically applied. CONT.. By comparing the vehicle’s actual yaw rate to the target yaw rate, the on-board computer can identify to what degree the vehicle may be under- or over-steering, and what corrective action, if any, is required. Corrective action may include reducing engine power as well as applying the brake on one or more wheels to realign the vehicle. Where is the Yaw Rate Sensor located? The yaw rate sensor is typically located under the driver or passenger seat, mounted on the level floorboard in order to access the vehicle’s center of gravity. After installation, a reset/recalibration procedure is generally required. E)Vehicle Speed Sensor The vehicle speed (VS) sensor is used by the EBCM to help control the suspension system. The vehicle speed sensor is a magnetic sensor and generates an analog signal whose frequency increases as the speed increases. The ride is made firmer at high speeds and during braking and acceleration and less firm at cruise speeds. F) Driver Selector Switch The driver selector switch is a two- or three-mode switch, usually located in the center console, and is an input to the suspension control module. The switch that is used to select either touring (soft) or performance (firm) ride is found on the Selectable Ride (SR) and the Computer Command Ride (CCR) systems. The mode select switch status is generally displayed on a scan tool. The three- position switch is used on the Corvette RTD system, and allows the driver to select three modes of operation: Tour Sport Performance CONT.. Driver selector switch G)Pressure Sensor A pressure transducer (sensor) is typically mounted on the compressor assembly. This sensor is typically found on suspension systems that use a compressor assembly. The main function of the pressure sensor is to provide feedback to the suspension control module about the operation of the compressor. The sensor assures both that a minimum air pressure is maintained in the system and that a maximum value is not exceeded. A pressure transducer (sensor) is typically mounted on the compressor assembly. This sensor is typically found on systems such as air suspension, real- time damping, and road-sensing suspension that use a compressor assembly. CONT.. The operation of the pressure sensor requires a 5-volt reference, a ground, and a signal wire to provide feedback to the control module. The voltage output on the signal wire will vary from 0 to 5 volts based upon pressure in the system. A high voltage indicates high pressure and low voltage indicates a low pressure. Pressure sensor with air compressor motor Actuators for Electronic Suspension system Actuators for electronic suspension systems are devices that change the ride height or damper stiffness of a vehicle to improve handling and ride comfort. They are typically electromagnetic or electro-hydraulic. Here are some types of actuators used in electronic suspension systems: Electromagnetic actuators: These actuators are popular because they have a quick response and simple structure. For example, an active seat suspension can use two electromagnetic linear actuators to reduce vibration. Hydraulic actuators: These actuators have a large output that can carry heavy mass. Electromechanical actuators: These actuators are made up of a brushless motor and a high ratio reduction gear that connects to the suspension arm. A central Electronic Control Unit (ECU) controls each actuator. Actuators work with sensors to identify road defects, vehicle speed, and cornering forces. The actuators then change the ride height or damper stiffness to adjust to the changing road conditions and driving demand CONT.. Air compressor motor  Air Compressor  Solenoids  Air Dryer Exhaust Solenoid The exhaust solenoid, which is located on the compressor, relieves pressure in the system. The ground-side switched exhaust solenoid has three main functions: 1.It releases compressed air from the shock absorbers or air springs to lower the vehicle body. 2.It relieves compressor head pressure. By exhausting air, it protects compressor start-up from high head pressure, which can possibly cause fuse failure. 3.The solenoid acts as a pressure relief valve, which limits overall system pressure. The special functions on many scan tools can be used to command the solenoid and to verify its operation. CONT.. Merits and Demerits of Electronic Suspension System Electronic suspension systems offer several advantages and disadvantages. Let's take a look at each: Merits of Electronic Suspension Enhanced Ride Comfort: Electronic suspension systems can adapt and adjust the suspension settings in real-time, resulting in improved ride comfort. The ability to soften or stiffen the suspension allows for better absorption of bumps and vibrations, providing a smoother and more comfortable ride for occupants. Improved Handling and Stability: By continuously monitoring and adjusting the suspension parameters, electronic suspension systems can enhance vehicle handling and stability. They can counteract body roll during cornering, minimize pitch and dive under acceleration and braking, and improve overall road holding capabilities, resulting in better control and confidence for the driver. CONT.. Adaptability to Different Road Conditions: Electronic suspension systems can automatically adapt to different road conditions, such as rough surfaces, potholes, or uneven terrain. They can adjust the damping characteristics to provide optimal suspension response, maintaining tire contact with the road and maximizing grip. Driver-Selectable Modes: Many electronic suspension systems offer driver-selectable modes, allowing the driver to choose different suspension settings to suit their preferences or specific driving conditions. This flexibility enables customization of the suspension characteristics, providing options for comfort-oriented or sportier driving experiences. Integration with Other Vehicle Systems: Electronic suspension systems can be integrated with other vehicle systems, such as stability control, adaptive cruise control, or active safety systems. By sharing sensor data and coordinating responses, these systems can work together to improve overall safety and performance. Demerits of Electronic Suspension Cost: Electronic suspension systems tend to be more expensive compared to traditional suspension systems. They involve additional components, such as sensors, control units, and actuators, which can increase the manufacturing and maintenance costs of the vehicle. Complexity: The increased complexity of electronic suspension systems can make them more challenging to diagnose and repair. The intricate network of sensors, control units, and actuators requires specialized knowledge and equipment for proper maintenance and troubleshooting. Reliability and Durability: Electronic suspension systems rely on various electronic components, which may be subject to wear, damage, or failure over time. The durability and long-term reliability of these systems can be a concern, and repairs or replacements can be costly. CONT.. Maintenance and Repairs: Maintaining and repairing electronic suspension systems may require specialized knowledge and expertise. If issues arise, it may be necessary to visit a qualified technician or dealership, potentially leading to higher maintenance costs compared to conventional suspension systems. Potential for Malfunctions: Like any electronic system, there is a possibility of malfunctions or software glitches in electronic suspension systems. These issues could potentially affect the performance or safety of the vehicle, requiring prompt attention and repairs. Unit Two Testing electronically controlled suspension system Testing Sensors and Actuators The issues and diagnostic techniques used for sensors and actuators are common to many systems. Testing sensors to diagnose faults is usually a matter of measuring their output signal. Testing Sensors A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an electronic control unit (ECU), an observer or an instrument. Most vehicle sensors produce an electrical signal, so checking their output on an oscilloscope is often the recommended method. However, many can also be checked using a multimeter. CONT.. Scope wave Sensor Type Test equipment Methods Results patterns  Values vary from approx. 200–400 Ω on  A resistance test with  Ohmmeter some vehicles to 800– Inductive the sensor  AC 1200 Ω on others. (Wheel speed disconnected Sine wave sensor) Voltmeter  The ‘sine wave’ output  AC voltage output with should be approx. 5 V the wheel rotating (less depending on engine speed) Hall effect  DC voltmeter  The voltage output  This distributor switches  Logic probe measured as the engine between 0 and approx. 8  Do NOT use or component is V as the Hall chip is an ohmmeter rotated slowly. magnetised or not. as this will  The sensor is normally  Others switch between damage the supplied with a 5 V or 0 and approx. 4 V Hall chip a 10–12 V  A logic probe will read high and low as the sensor output switches Optical  DC voltmeter  The device will  Clear switching between N/A normally be supplied low and high voltage with a stabilised voltage. Check the output wire signal as the device is rotated slowly Variable  DC voltmeter  This sensor is a  The voltage should resistance variable resistor. change smoothly from  If the supply is left approx. 0 V to the connected then check supply voltage (often 5 the output on a DC V) voltmeter Position sensor  DC voltmeter  The normal supply to  The output should NA an externally mounted change between approx. position sensor is 5 V. 0 and 5 V as the as there Check the output as is changes. As a manifold pressure general guide 2.5 V at changes either by idle speed snapping the throttle Testing Actuators There are many ways of providing control over variables in and around the vehicle. ‘Actuators’ is a general term used here to describe a control mechanism. When controlled electrically, they will work either by a thermal or by a magnetic effect. In this section, the term actuator will generally be used to mean a device which converts electrical signals into mechanical movement. Actuator Equipment Methods Results CONT.. Scope pattern Solenoid  Ohmmeter  Disconnect the component  The resistance of many and measure its resistance injectors is approx. 16 Ω (but check data). Motor  Battery supply  Most ‘motor’ type  Normal operation with actuators can be run from current draw appropriate  (fused) Ammeter a battery supply after they to the ‘work’ done by the device. For example, a  Are disconnected from the fuel pump motor may circuit. If necessary the draw up to 10 A, but an current draw can be idle actuator will only measured draw 1 or 2 A Solenoid actuator  Duty cycle Meter  Most types are supplied  The duty cycle will vary with a variable ratio as a change is required  Ohmmeter square wave disconnected from the circuit Stepper motor  Ohmmeter  Test the resistance of each  Winding resistances winding with the motor should be the same. disconnected from the Values in the region of circuit 10–20 Ω are typical Instrument display  Ohmmeter  Check the winding for  Continuity and slow continuity; if OK, power movement (several  Fused battery up the device and note its seconds to a few supply operation (for instruments, minutes) to close the power these but use a valve or move as resistor in place of the required sender unit) Testing hydraulic modulator Testing a hydraulic modulator for an electronic suspension system typically involves a combination of visual inspection, diagnostic scanning, and functional testing.  Visual Inspection: Start by visually inspecting the hydraulic modulator for any signs of damage, leaks, or loose connections. Check the wiring harness and connectors for any signs of damage or corrosion. Ensure that all components are securely mounted.  Diagnostic Scanning: Connect a diagnostic scanner or a specialized tool compatible with the electronic suspension system to the vehicle's on-board diagnostic (OBD) port. This will allow you to retrieve any fault codes stored in the system's control module. Fault codes can provide valuable information about specific issues or malfunctions related to the hydraulic modulator.  Functional Testing: Perform functional tests to assess the performance of the hydraulic modulator. Unit Three. Maintaining electronically controlled suspension systems Servicing electronically controlled Suspension systems  An active suspension system (also known as computerized ride control) has the ability to adjust itself continuously. It monitors and adjusts its characteristics to suit the current road conditions. As with all electronic control systems, sensors supply information to an ECU which in turn outputs to actuators. By changing its characteristics in response to changing road conditions, active suspension offers improved handling, comfort, responsiveness and safety.  Most electronic suspension servicing requires the removal and replacement of a components. The correct procedures for doing this are given in the manufacturer’s service information. Serviceable items include the air compressor, air compressor motor, solenoids, sensors, suspension control module, system wiring and power supply system. Servicing atomic level control o Vehicles that have an air inflator system as part of the automatic level control (ALC) system also have an air inflator switch. The air inflator switch is an input to the ALC and AS system. The inflator switch is used to control the air inflator system operation and provides a signal to the ALC or AS module to initiate compressor activation Inflator Or Compressor Relay o The suspension control module energizes the relay to activate the compressor motor. This adjusts the rear trim height as needed. The suspension control module controls the compressor relay for normal operation or for the accessory air inflator. To avoid compressor overheating, the timer within the suspension control module limits the compressor run time to 10 minutes. Air Dryer Within the compressor is an air dryer. The air dryer is responsible for removing moisture from the compressor system. Exhaust Solenoid The exhaust solenoid, which is located on the compressor, relieves pressure in the system. The ground-side switched exhaust solenoid has three main functions: 1. It releases compressed air from the shock absorbers or air springs to lower the vehicle body. 2. It relieves compressor head pressure. By exhausting air, it protects compressor start-up from high head pressure, which can possibly cause fuse failure. 3. The solenoid acts as a pressure relief valve, which limits overall system pressure. CONT.. Adjusting electronic controlled suspension  Electronic suspension systems utilize various actuators to adjust the suspension characteristics of a vehicle. The specific actuators used can vary depending on the design and implementation of the system, but here are some commonly employed actuators in electronic suspension systems: Solenoid Valves: Solenoid valves are commonly used in electronic suspension systems to control the flow of hydraulic fluid within the shock absorbers or dampers. By adjusting the opening and closing of the solenoid valves, the system can regulate the damping forces exerted on the suspension. Solenoid valves provide precise and rapid control over the damping characteristics. Carrying out road test If possible, perform a road test of the vehicle with the owner of the vehicle. It is also helpful to have the owner drive the vehicle. While driving, try to determine when and where the noise or suspension problem occurs. It’s also essential to record live data of the suspected component under testing for further analysis in the shop.

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