For 1990-2009 cars
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

### Circuit Description

The engine control module (ECM) functions as the central module for the controller area network (CAN) bus. The CAN consists of two separate conductors between the ECM and the transmission control module (TCM). Two additional conductors connect the ECM and the Electronic Brake/Traction Control Module (EBTCM). Each module sends information by toggling the circuits high or low to produce pulse-width signals, which the other modules decode.

The CAN data stream contains information such as status messages for relevant operating parameters, device requests and acknowledgments, and state-of-health messages.

When the TCM has not received ECM data for a specified amount of time, then DTC U2105 will set. DTC U2105 is a type B DTC.

### Condition for Running the DTC

The ignition is ON.

### Condition for Setting the DTC

The TCM has not received ECM messaging for 1 second.

### Action Taken When the DTC Sets

• | The TCM flashes the sport mode lamp and sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL.

• | The ECM records the operating conditions in the Freeze Frame at the time of the MIL request from the TCM.

• | The transmission operates in the default mode (maximum line pressure, command 4th gear, inhibit TCC, freeze shift adapts).

### Conditions For Clearing the MIL/DTC

• | The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request.

• | 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 MIL/DTC.

• | The TCM cancels the DTC default mode actions when the ignition switch is Off long enough in order to power down the TCM.

### 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).

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission ? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission
2 |

1. Install the Scan Tool .
2. Turn ON the ignition with the engine OFF.

Important: Record the Failure Records before clearing the DTCs. Using the Clear Info function erases the Failure Records from the ECM and the TCM.

3. Record the DTC Failure Records.
4. Clear the DTC.
5. Turn OFF the ignition for at least 30 seconds.
6. Turn ON the ignition with the engine OFF.

Did DTC U2105 reset?

--

Go to Step 3

Go to Intermittent Conditions in Engine Controls

3 | Did you record a Failure Record for DTC U2100? | -- | Go to DTC U2100 | Go to Step 4
4 | Did you record a Failure record for any ECM DTCs? | -- | Go to the applicable ECM DTC | Go to Step 5
5 | Replace the ECM. Refer to Engine Control Module Replacement . Is the action complete? | -- | Go to Step 6 | --
6 | Perform the following procedure in order to verify the repair:

1. Select DTC.
2. Select Clear Info.
3. Start the engine.

Did DTC U2105 reset?

--

Go to Step 1

System OK