Circuit Description
The controller area network (CAN) is used to receive and transmit data between the engine control module (ECM), the electronic brake/traction control module (EBTCM), and the transmission control module (TCM). Each module sends signals by toggling the circuit either high or low to produce pulse-width signals, which the other modules decode. Circuits XR888 and XY888 are the CAN information lines used to transmit the data between the modules.
The CAN data stream contains status messages for relevant operating parameters, as well as state-of-health messages.
When the TCM has not received an EBTCM data signal for a specified amount of time, then DTC U2108 will set. DTC U2108 is a type C DTC.
Condition for Running the DTC
The ignition switch is in the RUN position.
Condition for Setting the DTC
The TCM has not received EBTCM messaging for 1 second.
Action Taken When the DTC Sets
| • | The MIL will not illuminate. |
| • | The ECM records the operating conditions in the Failure Records at the time of the DTC request from the TCM. |
| • | The TCM memory stores the DTC at the time of the first failure. |
Conditions for Clearing the DTC
| • | A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic. |
| • | The scan tool clears the DTC. |
Diagnostic Aids
Use the J 35616 connector test adapter kit for any test that requires probing the TCM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.
Check for the following conditions:
| • | Poor connections at the TCM or at the component. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| Refer to General Electrical Diagnosis in Wiring Systems for proper procedure. |
| • | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving any related connectors and any wiring harnesses. A change in the display may help to locate the fault. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Transmission On-Board Diagnostic (OBD) System Check ? | -- | ||
Important: Before clearing the DTC, use the Scan Tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the ECM/TCM. Did DTC U2108 reset? | -- | Go to Diagnostic Aids | ||
3 |
Does the Scan Tool transmit live EBTCM data values? | -- | Go to Diagnostic Aids | |
4 | Check circuit XR 888 and XY 888 for an short to ground. Refer to General Electrical Diagnosis in Wiring Systems. Did you find the condition? | -- | ||
5 | Check circuit XR 888 and XY 888 for an open. Refer to General Electrical Diagnosis in Wiring Systems. Did you find the condition? | -- | ||
6 | Repair the wiring as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
7 | Replace the TCM. Refer to Transmission Control Module Replacement . Did you complete the replacement? | -- | -- | |
8 | Perform the following procedure in order to verify the repair:
Does the Scan Tool transmit live EBTCM data values? | -- | System OK |
