Circuit Description
Modules connected to the controller area network (CAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. If no communication is detected on CAN serial data circuit, the DTC is set. A total non communication condition may be caused by a short to battery or voltage on any of the CAN circuits or a short between the CAN high and low circuits.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC U2105 Lost Communication With Engine Control Module (ECM) |
| • | DTC U2106 Lost Communication With Transmission Control Module (TCM) |
| • | DTC U2107 Lost Communication With Body Control Module (BCM) |
| • | DTC U2108 Lost Communication With Electronic Brake Control Module (EBCM) |
Conditions for Running the DTCs
| • | Voltage supplied to the modules is in the normal operating voltage range. |
| • | The vehicle power mode requires serial data communication to occur. |
| • | The DTC U2100 does not have a current status. |
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received.
Action Taken When the DTC Sets
The module uses a default value for the missing parameter.
Conditions for Clearing the DTC
| • | A current DTC clears when the malfunction is no longer present. |
| • | A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction. |
Diagnostic Aids
Important: The scan tool communicate with the BCM on class 2 bus and on Keyword 2000 bus for the rest of modules that functionally communicate on CAN bus. The above DTCs are set for communication among modules on CAN bus. For example, if DTC U2108 is set, the scan tool may communicate properly with the EBCM, but EBCM may not functionally communicate properly on CAN bus. Refer to Data Link Communications Description and Operation .
| • | A poor connection at the inoperative module may cause this code to set. |
| • | An improperly powered module may cause this code to set. |
Step | Action | Yes | No | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Data Communication Schematics Connector End View Reference: Data Communication Connector End Views | |||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||||||||||
2 |
Important: Use the DTC list in DTC Descriptors to determine which is the module that is not communicating on CAN bus. Test the following circuits of the module that is not communicating on controller area network (CAN) bus for an open or a short to ground:
Refer to the following:
Did you find and correct the condition? | Go to Step 7 | Go to Step 3 | ||||||||||||||||
3 |
Refer to the following:
Did you find and correct the condition? | Go to Step 7 | Go to Step 4 | ||||||||||||||||
4 | Test the CAN serial data circuits of the module that is not communicating for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 7 | Go to Step 5 | ||||||||||||||||
5 | Inspect the harness connectors of the module that is not communicating on CAN bus for poor connections and terminal tension at the following circuits:
Refer to the following:
Did you find and correct the condition? | Go to Step 7 | Go to Step 6 | ||||||||||||||||
6 | Replace the module that is not communicating on CAN bus. Refer to Control Module References for replacement, setup and programming. Did you complete the replacement? | Go to Step 7 | -- | ||||||||||||||||
7 | Use the scan tool in order to clear the DTCs. Does the scan tool still display other current DTCs? | -- | |||||||||||||||||
