GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC K Sierra - 4WD (CNG) 🢒 DTC 🢒 DTC P0600

Circuit Description

The Alternative Fuels ECM communicates via the Class 2 serial data circuit. The Alternative Fuels ECM monitors this circuit for activity. If the Alternative Fuels ECM does not receive or send a message on the Class 2 circuit for 10 seconds, this DTC sets.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC
    • The Alternative Fuels ECM does not receive, or send, a Class 2 message.
    • The condition exists for 10 seconds.

Action Taken When the DTC Sets

The Alternative Fuels ECM records the operating conditions at the time the diagnostic fails. The Alternative Fuels ECM stores this information in the Freeze Frame and/or Failure Records.

Conditions for Clearing the MIL/DTC
    • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
    • A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Use a scan tool in order to clear the DTC.

Test Description

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

  1. This step determines if the condition is present.

    2.

  2. This step determines if the condition affects other control modules.

    3.

  3. This step determines if the condition is causing a no start.

    4.

  4. This step determines if the Alternative Fuels ECM is the cause of the condition. If the scan tool displays other module information with the Alternative Fuels ECM disconnected, replace the Alternative Fuels ECM.

    5.

  5. This step determines if the class 2 serial data circuit between the Alternative Fuels ECM and the splice pack is grounded. If the circuit is not grounded, refer to the information in Data Link Communications in order to diagnose the rest of the class 2 circuits and modules.

    6.

  6. This step determines if a fuse that supplies voltage to the Alternative Fuels ECM is open. If a fuse is open, test the circuit and all related components for a short to ground.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

2

With a scan tool, attempt to communicate with the Alternative Fuels ECM.

Does the scan tool display Alternative Fuels ECM data?

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame and/or Failure records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame and/or Failure records data that you observed.

Does the DTC fail this ignition?

Go to Step 4

Go to Intermittent Conditions

4

Attempt to establish communication with the listed control modules. If you are using a Tech 2, obtain the information with the Class 2 Message Monitor feature:

    • The instrument panel cluster (IPC)
    • The powertrain control module (PCM)
    • The vehicle theft deterrent (VTD)

Does the scan tool communicate with all of the listed control modules?

Go to Step 5

Go to Step 6

5

Attempt to start the engine.

Does the engine start and idle?

Go to Step 7

Go to Step 9

6

  1. Turn OFF the ignition.
  2. Disconnect the Alternative Fuels ECM connector C001. Refer to Alternative Fuels Engine Control Module Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Attempt to establish communication with the listed control modules.
    5. • IPC
    • PCM
    • VTD

Does the scan tool communicate with all the listed control modules?

Go to Step 15

Go to Step 8

7

Test the class 2 serial data circuit for the following:

    • An open circuit between the Alternative Fuels ECM and the splice pack SP205.
        Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.
    • Proper connection at the Alternative Fuels ECM or the splice pack SP205.
        Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 16

Go to Step 15

8

Test the class 2 serial data circuit for a short to ground between the Alternative Fuels ECM and the splice pack SP205. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 16

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications in the C/K Pickup Service Manual

9

Inspect the following fuses.

    • IGN 0
    • IGN E
    • ECM B

Are any of the listed fuses open?

Go to Step 10

Go to Step 11

10

Test the affected circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 16

Go to Step 15

11
  1. Turn OFF the ignition.
  2. Disconnect the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Probe each voltage supply circuit of the Alternative Fuels ECM with a test lamp connected to a known good ground.

Does the test lamp illuminate for each circuit?

Go to Step 12

Go to Step 14

12

Probe each ground circuit of the Alternative Fuels ECM with a test lamp connected to B+.

Does the test lamp illuminate for each circuit?

Go to Step 13

Go to Step 14

13

Inspect for proper connections at the harness connectors of the Alternative Fuels ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 16

Go to Step 15

14

Repair the circuit that did not illuminate the test lamp. Refer to Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you complete the repair?

Go to Step 16

--

15

Replace the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement .

Did you complete the replacement?

Go to Step 16

--

16
  1. Use the scan tool in order to clear the DTCs from the following control modules:
    2. • Alternative Fuels ECM
    • PCM
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 17

Go to Step 2

17

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK