For 1990-2009 cars

### Description

The DTC P0601 Control Module Read Only Memory sets when the powertrain control module (PCM) has detected a failure in the communication circuitry.

### Condition for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

An error was detected in the electrically erasable programmable read only memory (EEPROM) data readout.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after 3 consecutively passing trips without a fault present.

• | A history DTC clears after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool Clear DTC Information function.

### Diagnostic Aids

Check the PCM for water contamination. Water entering the PCM can cause damage and corrosion to the circuit boards and to internal components. Repair the source of the water entry before the installation of a replacement PCM.

A DTC P0601 can set if an incorrect PCM is installed in the vehicle. Install the correct PCM according to the vehicle and/or the engine type and equipment options.

### Test Description

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

1. The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step determines if the fault is present. Replace the PCM if this DTC sets again.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 | Important: If the vehicle does not start, crank the engine in order to allow the DTC to set.

1. Install a scan tool.
2. Clear the scan tool information.
3. Turn OFF the ignition, in order to initialize the powertrain control module (PCM).
4. Start the engine.
5. Road test the vehicle.

Does the scan tool indicate a DTC P0601?

Go to Step 3

Go to Diagnostic Aids

3 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | Go to Step 4 | --
4 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 5

Go to Step 2

5 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | Go to Diagnostic Trouble Code (DTC) List | System OK