For 1990-2009 cars

### Circuit Description

The internal fault detection is handled inside the transmission control module (TCM). No external circuits are involved.

### DTC Descriptors

This diagnostic procedure supports the following DTCs:

• | DTC P0601 Transmission Control Module (TCM) Read Only Memory (ROM)

• | DTC P0602 Transmission Control Module (TCM) Not Programmed

• | DTC P0603 Transmission Control Module (TCM) Long Term Memory Reset

• | DTC P0604 Transmission Control Module (TCM) Random Access Memory (RAM)

### Conditions for Running the DTC

The TCM runs the program to detect an internal fault when the engine is running. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

### Conditions for Setting the DTC

The TCM has detected an internal malfunction.

### Action Taken When the DTC Sets

• | The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).

• | The TCM commands a soft landing to 2nd gear: P0601, P0603, and P0604.

• | The TCM commands an immediate landing to 2nd gear: P0602.

• | The TCM commands maximum line pressure.

• | The TCM forces the TCC solenoid OFF.

• | The TCM inhibits TCC engagement.

• | The TCM freezes transmission adaptive functions.

• | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.

• | The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame.

### Conditions for Clearing the MIL/DTC

• | The TCM turns off the MIL after the third consecutive trip in which the diagnostic test runs and passes.

• | A scan tool can clear the DTC.

• | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.

• | The TCM cancels the DTC default actions when the ignition 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. A DTC P0602 indicates the TCM is not programmed.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Is DTC P0602 set? | Go to Step 3 | Go to Step 5
3 | Program the TCM. Refer to Control Module References for replacement, setup, and programming. Does DTC P0602 reset? | Go to Step 4 | Go to Step 6
4 |

1. Ensure that all tool connections are secure.
2. Ensure the programming equipment is operating correctly.
3. Ensure the correct software/calibration package is used.
4. Attempt to program the TCM. Refer to Control Module References for replacement, setup, and programming.

Does DTC P0602 reset?

Go to Step 5

Go to Step 6

5 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | --
6 | Perform the following in order to verify the repair:

1. Select the DTC.
2. Select Clear Info.
3. Start the engine.
4. Select specific DTC, for the DTC that was set.

Has the test run and passed?

Go to Step 7

Go to Step 2

7 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTC's that you have not diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK