For 1990-2009 cars

## DTC P0602 3.0L (L81)

### Circuit Description

A normal function of the transmission control module (TCM) is to perform an internal test that verifies the security of the diagnostic and control calibration programming. The programming must contain security codes that enable a software lock to engage. The software lock is designed to prevent unauthorized changes to the diagnostics or control calibrations. The software lock utility is processed independently from the diagnostic and control calibration software and contains application specific data. The software lock data is entered into the TCM during the final assembly of the vehicle.

When the security codes from the diagnostic and shift calibration software fail to engage the software lock, the TCM sets DTC P0602. DTC P0602 is a type A DTC.

### Conditions for Running The DTC

• | No TCM DTC P0601.

• | The engine is running.

### Conditions for Setting The DTC

The TCM detects an unlocked calibration memory range.

### Action Taken When the DTC Sets

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

• | The TCM commands maximum line pressure.

• | The TCM freezes transmission adaptive functions.

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

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

• | The TCM stores DTC P0602 in TCM history.

### Conditions for Clearing the MIL/DTC

• | The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.

• | A scan tool can clear the MIL/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 default actions when the ignition switch is OFF long enough in order to power down the TCM.

### Diagnostic Aids

DTC P0602 may set as a result of TCM reprogramming.

### Test Description

The number below refers to the step number on the diagnostic table.

1. This step eliminates the TCM software as a possible cause of the DTC. If the DTC continues to set after reprogramming, the fault is in the TCM hardware.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls - 3.0L (L81)
2 |

1. Install a scan tool.
2. Turn ON the ignition with the engine OFF.

Important:

• | Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from both the ECM and the TCM.

• | Record the DTC Freeze Frame and Failure Records.

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.

Did DTC P0602 reset?

--

Go to Step 3

Go to Diagnostic Aids

3 | Perform the Transmission Control Module Reprogramming Procedure. Refer to Service Programming System (SPS) in Vehicle Control Systems. Did the DTC P0602 reset? | -- | Go to Step 4 | Go to Step 5
4 | Replace the TCM. Refer to Transmission Control Module Replacement Is the replacement complete? | -- | Go to Step 5 | --
5 | Perform the following procedure in order to verify the repair:

1. Select DTC.
2. Select Clear Info.
3. Turn OFF the ignition for at least 30 seconds.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
5. Select Specific DTC.
6. Enter DTC P0602.

Has the test run and passed?

--

Go to Step 6

Go to Step 2

6 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 3.0L (L81) | System OK