For 1990-2009 cars

## DTC P0603 3.0L (L81)

### Circuit Description

A normal function of the transmission control module (TCM) is to perform an internal test that verifies the integrity of the non-volatile random access memory (NVRAM) allocation. This diagnostic detects faults in the allocation of NVRAM that contain the transmission adaptive memory cells by comparing a calculated checksum with a stored checksum. When the TCM detects that the calculated checksum is different from the stored checksum, DTC P0603 sets. DTC P0603 is a type A DTC.

### Conditions for Running The DTC

• | No TCM DTC P0604.

• | The engine is running.

### Conditions for Setting The DTC

The TCM NVRAM checksums do not match.

### 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 P0603 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.

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 P0603 reset?

--

Go to Step 3

Go to Diagnostic Aids

3 | Replace the TCM. Refer to Transmission Control Module Replacement Is the replacement complete? | -- | Go to Step 4 | --
4 | 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 P0603.

Has the test run and passed?

--

Go to Step 5

Go to Step 2

5 | 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