For 1990-2009 cars

### Circuit/System Description

This diagnostic applies to internal microprocessor integrity conditions within the engine control module (ECM). This diagnostic also addresses if the ECM is not programmed.

### DTC Descriptors

This diagnostic procedure supports the following DTCs:

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

• | DTC P0602 Control Module Not Programmed

• | DTC P0603 Control Module Long Term Memory Reset

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

• | DTC P0606 Control Module Internal Performance

### Conditions for Running the DTC

#### P0601

• | The checksum calculation at power down in the last drive cycle completely finished.

| OR

• | Part checksum value is on a changable state.

• | One of the above conditions exists for 30 seconds, DTC P0601 continues once.

#### P0602

Turn the ignition switch ON, with the engine OFF. DTC P0602 runs continuously.

#### P0603

• | The read/write test at power down in the last drive cycle completely finished.

• | DTC P0604 runs continuously once the above conditions exist for more than 5 seconds.

#### P0604

• | The read/write test at power down in the last drive cycle completely finished.

• | DTC P0604 runs continuously once the above conditions exist for more than 5 seconds.

#### P0606

• | The read/write test at power down in the last drive cycle completely finished.

• | DTC P0606 runs continuously once the above conditions exist for more than 5 seconds.

### Conditions for Setting the DTC

#### P0601

The ECM detects the incorrect read only memory (ROM) checksum for more than 4 seconds.

#### P0602

The ECM detects that programming is incomplete for more than 4 seconds.

#### P0603

The ECM detects an internal condition for more than 4 seconds.

#### P0604

The ECM detects random access memory (RAM) errors for more than 4 seconds.

#### P0606

The ECM detects an internal condition for more than 4 seconds.

### Action Taken When the DTC Sets

• | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

### Conditions for Clearing the DTC

• | The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A current DTC, last test failed, clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Clear the MIL and the DTC with a scan tool.

### Diagnostic Aids

For complete details on programming the ECM, refer to Control Module References for replacement, setup, and programming.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. DTC P0602 indicates the ECM is not programmed.

2. Attempt to program the ECM. If the ECM fails to program a second time, replace the ECM.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Did DTC P0341, P0346, P0366, or P0391 fail this ignition? | Go to Step 3 | Go to Step 5
3 | Did DTC P0342, P0343, P0347, P0348, P0367, P0368, P0392, or P0393 also fail this ignition cycle? | 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 and the correct calibration is used.
4. Attempt to program the ECM. 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 ECM. Refer to Control Module References for replacement, setup, and programming. Did you find and correct the condition? | Go to Step 6 | --
6 |

1. Clear any DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

Go to Step 2

Go to Step 7

7 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK