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Questions and Answers
A high-speed CAN BUS communicates with a scan tool through which terminal(s)?
A high-speed CAN BUS communicates with a scan tool through which terminal(s)?
UART uses a ________ signal that toggles OV.
UART uses a ________ signal that toggles OV.
5 volts
Which terminal of the OBD-II data link connector is the chassis ground for all vehicles?
Which terminal of the OBD-II data link connector is the chassis ground for all vehicles?
4
Which technician is correct regarding Chrysler OBD-I (1981—1995) vehicles and their BUS system?
Which technician is correct regarding Chrysler OBD-I (1981—1995) vehicles and their BUS system?
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The UART data BUS operates at a baud rate of ________ bps.
The UART data BUS operates at a baud rate of ________ bps.
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Which technician is correct regarding a break-out box (BOB) and diagnostic connectors?
Which technician is correct regarding a break-out box (BOB) and diagnostic connectors?
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Which of these is commonly designated D2B and connects various components in a single-ring structure?
Which of these is commonly designated D2B and connects various components in a single-ring structure?
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GM Class 2 communication toggles between ________ and ________ volts.
GM Class 2 communication toggles between ________ and ________ volts.
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Which terminal of the data link connector does General Motors use for Class 2 communication?
Which terminal of the data link connector does General Motors use for Class 2 communication?
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Low-speed networks operate at less than ________ bits per second.
Low-speed networks operate at less than ________ bits per second.
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A module is also known as a ________.
A module is also known as a ________.
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Which technician is correct regarding module communications networks?
Which technician is correct regarding module communications networks?
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Which terminal of the OBD-II data link connector is the signal ground for all vehicles?
Which terminal of the OBD-II data link connector is the signal ground for all vehicles?
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Which of these is a version of Byteflight and is a high-speed serial communication system?
Which of these is a version of Byteflight and is a high-speed serial communication system?
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Which of these is a single-wire serial communications protocol?
Which of these is a single-wire serial communications protocol?
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Which technician is correct about a CANDi module and a twisted pair?
Which technician is correct about a CANDi module and a twisted pair?
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An OBD-I Ford is able to provide engine serial data if there are terminals in which cavities of the DLC?
An OBD-I Ford is able to provide engine serial data if there are terminals in which cavities of the DLC?
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GMLAN is the General Motors term for which type of module communication?
GMLAN is the General Motors term for which type of module communication?
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Terminal 16 of the OBD-II data link connector is used for what?
Terminal 16 of the OBD-II data link connector is used for what?
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The process of sending multiple signals of information at the same time over a signal wire is called?
The process of sending multiple signals of information at the same time over a signal wire is called?
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Why is a gateway module used?
Why is a gateway module used?
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What are U codes?
What are U codes?
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How do CAN H and CAN L operate?
How do CAN H and CAN L operate?
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Study Notes
OBD-II and Communication Protocols
- High-speed CAN BUS communicates through terminals 6 and 14.
- Class 2 communication in GM vehicles uses terminal 2 of the data link connector.
- OBD-II uses terminal 4 for chassis ground and terminal 5 for signal ground in all vehicles.
- A breakout box (BOB) accesses BUS terminals while using a scan tool; common in BMW and Mercedes with a 38-cavity diagnostic connector.
Protocols and Baud Rates
- UART operates at a baud rate of 8192 bps and toggles at 5 volts.
- Low-speed networks function at less than 10,000 bits per second.
- Domestic Digital BUS connects multiple components in a single-ring structure with speeds up to 5,600,000 bps.
Module Communication
- Chrysler OBD-I vehicles (1981-1995) utilized Serial Communications Interface (SCI), while Chrysler PCI is a three-wire protocol at terminal 2 of OBD-II.
- GMLAN is General Motors' term for high-speed CAN communication.
- Modules, or nodes, reduce wiring complexity and facilitate data sharing across sensors and different modules.
Signal Variations
- GM Class 2 communication toggles between 0 and 7 volts.
- CAN H and CAN L maintain voltage at 2.5 volts when not transmitting; CAN H rises to 3.5 volts when active.
Additional Concepts
- Flexray BUS is a high-speed serial communication system and a version of Byteflight.
- Motorola Interconnect (MI) is a single-wire protocol with one master and multiple slave modules.
- Multiplexing allows multiple information signals to be sent simultaneously over a single wire.
Gateway Module and Diagnostic Codes
- The gateway module acts as a primary communication module for scan tool data, typically found in IPC or body control modules.
- U codes represent diagnostic trouble codes related to network communication, helping to identify malfunctioning modules or circuits.
Studying That Suits You
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Description
Test your knowledge with flashcards focused on Chapter 49 of Automotive Technology. This chapter covers essential components of automotive communication systems including CAN BUS and UART. Perfect for aspiring automotive technicians and students in the field.
