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). 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 P0607 Control Module Internal Performance

Conditions for Running the DTC

P0601

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

P0602

    • The ignition is ON, with the engine OFF.
    • DTC P0602 runs once an ignition cycle.

P0607

    • The ignition is ON, with the engine OFF.
    • The ignition 1 voltage is more than 11 volts.
    • DTC P0607 runs continuously with ignition ON or engine operating.

Conditions for Setting DTC

P0601

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

P0602

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

P0607

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

Action Taken When the DTC Sets

P0601 or P0602

    • 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 Freeze Frame/Failure Records.

P0607

    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the MIL/DTC

P0601 or P0602

    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 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.

P0607

    • 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 non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Test Description

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

  1. A 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.

DTC P0601, P0602, or P0607

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

Is DTC P0602 set?

Go to Step 3

Go to Step 5

3

Program the engine control module (ECM).

Does DTC P0602 reset?

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.

Does DTC P0602 reset?

Go to Step 5

Go to Step 6

5

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

Go to Step 6

--

6

  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. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did 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

System OK