For 1990-2009 cars

### Description

The powertrain control module (PCM) has detected a failure in the communication circuitry.

### Conditions for Setting the DTC

An error was detected in the EEPROM data.

### Action Taken When the DTC Sets

• | The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM will record operating conditions at the time that the diagnostic fails. The Freeze Frame buffer stores this information.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after three consecutive passing trips without a fault present.

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

• | Use the Clear DTC Information function on the scan tool, or disconnect the PCM battery feed in order to clear the DTC.

### Diagnostic Aids

Check the PCM for water contamination. Water that is entering the PCM can cause damage and corrosion to the circuit boards and to internal components. Before the installation of a replacement PCM, repair the source of the water entry.

### Test Description

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

1. The Powertrain OBD System Check prompts the technician to complete some basic checks, and to save the applicable Freeze Frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.

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

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
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 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. Perform the Clear DTC Information function on the scan tool, and road-test the vehicle within the Freeze Frame conditions which set the DTC.
2. Review the scan tool data, and check the data for DTCs. The repair is complete if no DTCs are displayed.

Are any DTCs displayed on the scan tool?

--

Go to the applicable DTC table

System OK