GM Service Manual Online
For 1990-2009 cars only

Description

The engine control module (ECM) has detected a failure in the communication circuitry.

Conditions for Setting the DTC

An error was detected in the EEPROM data readout.

Action Taken When the DTC Sets

    • The ECM illuminates the malfunction indicator lamp (MIL).
    • The ECM 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 three consecutively passing trips without a fault present.
    • A History DTC clears after 40 consecutive warm-up cycles without a fault.
    • Use the scan tool Clear DTC Information function or disconnect the ECM battery feed in order to clear the DTC.

Diagnostic Aids

Check the ECM for water contamination. Water entering the ECM 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 ECM.

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 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 ECM 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 ECM.
  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 ECM. Refer to Engine Control Module Replacement.

Is the action complete?

--

Go to Step 4

--

4

  1. Perform the scan tool Clear Information function and road test the vehicle within the Freeze Frame conditions that set the DTC.
  2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to the Applicable DTC Table

System OK