The Controller Area Network (CAN) serial data circuit is a high speed serial data bus used to communicate information between the Electronic Brake and Traction Control Module (EBTCM), the Engine Control Module (ECM) and the Transmission Control Module (TCM). When the ignition switch is turned to the ON position, the modules begin to transmit data between each other. The following data is transmitted and received between the ECM and TCM:

The following data is transmitted and received between the ECM and EBTCM:

The addressing scheme employed with CAN assigns a label to every message, with each message receiving a unique "identifier". The identifier classifies the content of the message (such as engine speed). Each module processes only those messages whose identifiers are stored in the module's acceptance list. This is CAN's form of message filtering.

The identifier labels both the data content and the priority of the message being sent. Each module can begin transmitting its most important data as soon as the bus is unoccupied. When more than one module starts to transmit simultaneously, the message with the highest priority is assigned first access. A module responds to failure to gain access by automatically switching to receive mode, the module then repeats the transmission attempt as soon as the bus is free again.

The CAN Bus circuit is monitored continuously after the ignition switch is turned to the ON position.

Each controller on the CAN Bus monitors the CAN Bus circuit for the following malfunctions:

The following describes the action taken when the code is set in a particular control module.

Engine Control Module

Transmission Control Module

Electronic Brake Traction Control Module

The following describes the conditions for clearing the MIL/DTC in a particular control module.

Engine Control Module

Transmission Control Module

Electronic Brake Traction Control Module

The malfunction for this DTC will be limited to the control module that the DTC was set in, and the CAN Bus circuit(s) and controller(s) that are connected to the control module the DTC was set in.

It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.

Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM or TCM harness connector. Using this kit will prevent damage to the harness connector terminals.

Thoroughly inspect any circuitry that may be causing the complaint for the following conditions:

If an intermittent malfunction exists, refer to Intermittents and Poor Connections Diagnosis in Wiring Systems for further diagnosis.

The number(s) below refer to the step number(s) on the diagnostic table.

8. At this point, the most likely cause of the malfunction is the ECM, TCM or the EBTCM. This test will determine through process of elimination which module is causing the malfunction.

13. Because of the previous testing, the modules on the CAN Bus circuit may have set other CAN Bus DTCs. You must clear or diagnose the DTCs from these modules to avoid future misdiagnosis.