GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 GMC K Pickup - 4WD (CNG) 🢒 DTC 🢒 DTC P0601 Control Module Read Only Memory (ROM)

Circuit Description

The AF ECU contains data storage areas. The AF ECU runs a test on the stored data called a checksum. This DTC is used to indicate a failure has occurred within the AF ECU.

Conditions for Running the DTC

The ignition switch is ON.

Conditions for Setting the DTC

The AF ECU monitors an internal malfunction.

Action Taken When the DTC Sets

The AF ECU will switch-over to gasoline fuel operation. The AF ECU will not attempt alternative fuel operation until the next ignition key cycle.

    • The AF ECU will illuminate the MIL and store the DTC as History during ONE drive trip in which the diagnostic runs and fails.
    • The AF ECU will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data.

Conditions for Clearing the MIL/DTC

    • The Last Test Failed status will clear when the DTC runs and passes.
    • The AF ECU will turn OFF the MIL after 3 consecutive drive trips that the DTC runs and passes.
    • The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC.
    • All DTC Information can be cleared using a scan tool.
    • Interruption of Control Module (AF ECU / VCM / PCM or ECM) power or ground MAY clear DTC Information. Clearing DTC Information with this method is inconsistent and should not be performed.

Test Description

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

  1. Any failure of the AF ECU internal tests that results in this DTC being set requires that the AF ECU be replaced.

Step

Action

Value(s)

Yes

No

1

Did you perform the AF Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Alternative Fuels (AF) Powertrain On Board (OBD) System Check

2

  1. Replace the AF ECU. Refer to AF ECU Replacement.
  2. Program (flash) the replacement control module with the correct vehicle software and calibration.

Is the replacement complete?

--

Go to Step 3

--

3
  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches normal operating temperature.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number that was set.
  6. Operate the vehicle within the Conditions for Setting the DTC until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

--

System OK

Go to Alternative Fuels (AF) Powertrain On Board (OBD) System Check