For 1990-2009 cars

### DTC Descriptor

DTC P0601: Control Module Read Only Memory (ROM) Error
DTC P0602: Program Electronic Control Unit (ECU)
DTC P0604: Control Module Random Access Memory (RAM)
DTC P0606: Control Module Internal Performance

### Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle.

### 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.

### Conditions for Running the DTC

#### DTC P0601

The checksum calculation at power down in the last drive cycle has completely finished. DTC P0601 runs once an ignition cycle.

#### DTC P0602

The ignition is ON, with the engine OFF. DTC P0602 runs continuously.

#### DTC P0604

The read/write test at power down in the last drive cycle has completely finished. DTC P0604 runs once an ignition cycle.

#### DTC P0606

DTC P0606 runs continuously with ignition ON, engine running.

### Conditions for Setting the DTC

#### DTC P0601

The ECM detects the incorrect read only memory (ROM) checksum for more than 30 seconds.

#### DTC P0602

The ECM detects that programming is incomplete for more than 1 second.

#### DTC P0604

The ECM detects random access memory (RAM) errors for more than 5 seconds.

#### DTC P0606

The ECM detects an internal condition for more than 5 seconds.

### Action Taken When the DTC Sets

DTCs P0601, P0602, P0604 and P0606 are type A DTCs.

### Conditions for Clearing the DTC

DTCs P0601, P0602, P0604 and P0606 are type A DTCs.

### Reference Information

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

### Circuit/System Verification

• | Ignition ON, observe the DTC information with a scan tool. DTC P0601, P0602, P0604 and P0606 should not set.

• | If DTC P0601 or P0604 failed this ignition, replace the ECM.

### Circuit/System Testing

#### P0602

Program the ECM. If DTC P0602 sets after programming, perform the following steps:

• | Ensure that all tool connections are secure.

• | Ensure the programming equipment is operating correctly.

• | Ensure the correct software and the correct calibration is used.

• | Attempt to program the ECM.

⇒ | If DTC P0602 sets, replace the ECM.

#### P0606

1. Using a scan tool, observe the Freeze Frame/Failure Records.
2. Using a scan tool clear all DTCs.
3. Ignition OFF for 30 seconds.
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.

⇒ | If DTC P0606 failed this ignition, replace the ECM.

### Repair Instructions

• | Perform the Diagnostic Repair Verification.

• | Engine Control Module Replacement for engine control module replacement, setup and programming.