GM Service Manual Online
For 1990-2009 cars only

Circuit Description

This diagnostic applies to internal microprocessor integrity conditions within the engine control module (ECM).

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC P0601 Control Module Read Only Memory (ROM)
    • DTC P0604 Control Module Random Access Memory (RAM)
    • DTC P0605 Control Module Programming Read Only Memory (ROM)

Conditions for Running the DTC

DTC P0601

    • The ignition is ON, with the engine OFF or the engine is operating.
    • DTC P0601 runs once an ignition cycle.

DTC P0604

    • The ignition is ON, with the engine OFF or the engine is operating.
    • DTC P0604 runs once an ignition cycle.

DTC P0605

    • The ignition is ON, with the engine OFF or the engine is operating.
    • DTC P0605 runs once an ignition cycle.

Conditions for Setting DTC

DTC P0601

The ECM detects that the checksum calculation does not match the expected checksum.

DTC P0604

The ECM detects an internal condition for more than 3 seconds.

DTC P0605

The ECM detects an internal condition for more than 3 seconds.

Action Taken When the DTC Sets

    • The malfunction indicator lamp (MIL) will not illuminate.
    • The ECM will store conditions which were present when the DTC was set as Failure Records data only.
    • This information will not be stored in the Freeze Frame data.

Conditions for Clearing the MIL/DTC

    • The DTC clears when the diagnostic runs and passes.
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for more than 10 seconds.

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

Replace the engine control module (ECM). Refer to Engine Control Module Replacement.

Did you complete the replacement?

Go to Step 3

--

3

  1. Clear the 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.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 4

4

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK