For 1990-2009 cars
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The controller area network (CAN) is used to receive and transmit data (signal) between engine control module (ECM), the electronic brake/traction control module (EBTCM) and the transmission control module (TCM). The data is constantly being sent back and forth between the modules transferring information from their different inputs, reporting state-of-health, and supplying status messaging. Each module sends signals by toggling the circuit either high or low to produce pulse-width signals which the module decodes. Circuits XR888 and XY888 are the CAN information lines used to transmit the data between the modules.

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 D 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 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-A 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.

1. Performing this step verifies that an operational abnormality did not take place during TCM power-up, such as Electromagnetic Interference (EMI).

#### DTC U2108 Lost Communications with ABS/TCS Control System

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to On-Board Diagnostic System Check
2 |

1. Install the Scan Tool .
2. With the engine OFF, turn the ignition switch to the RUN position.

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.

3. Record the DTC Failure Records.
4. Clear the DTC.
5. Turn the ignition switch to the OFF position for at least 30 seconds.
6. With the engine OFF, turn the ignition switch to the RUN position.

Did DTC U2108 reset?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Start the engine.
2. Observe the Scan Tool Transmission Data display.

Does the Scan Tool transmit live EBTCM data values?

--

Go to Diagnostic Aids

Go to Step 4

4 | Check circuit XR 888 and XY 888 for an short to ground. Refer to General Electrical Diagnosis in Wiring Systems. Was the condition found? | -- | Go to Step 6 | Go to Step 5
5 | Check circuit XR 888 and XY 888 for an open. Refer to General Electrical Diagnosis in Wiring Systems. Was the condition found? | -- | Go to Step 6 | Go to Step 7
6 | Repair the wiring as necessary. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 8 | --
7 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the replacement complete? | -- | Go to Step 8 | --
8 | Perform the following procedure in order to verify the repair:

1. Select DTC.
2. Select Clear Info.
3. Start the engine.
4. Observe the Scan Tool Transmission Data display.

Does the Scan Tool transmit live EBTCM data values?

--

System OK

Go to Step 1