GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC K Sierra - 4WD (LPG) 🢒 DTC 🢒 DTC P0201, P0202, P0203, P0204, P0205, P0206, P0207, or P0208

Circuit Description

The Alternative Fuels ECM enables the appropriate fuel injector on the intake stroke for each cylinder. An ignition voltage is supplied to the fuel injectors through a fuel injector relay. The Alternative Fuels ECM controls each fuel injector by grounding the control circuit via a solid state device called a driver. The Alternative Fuels ECM monitors the status of each driver. If the Alternative Fuels ECM detects an incorrect voltage for the commanded state of the driver, a fuel injector control DTC sets.

Conditions for Running the DTC

The engine is operating on CNG.

Conditions for Setting the DTC
    • The Alternative Fuels ECM detects an incorrect voltage on a fuel injector control circuit.
    • The condition exists for 5 seconds.

Action Taken When the DTC Sets
    • The Alternative Fuels ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • 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.
    • The Alternative Fuels ECM will switch over to gasoline operation (KL6).

Conditions for Clearing the MIL/DTC

    • The Last Test Failed status will clear when the DTC runs and passes.
    • The Alternative Fuels ECM 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 with a scan tool.

Diagnostic Aids
    • Performing the Fuel Injector Coil test may help isolate an intermittent condition. Refer to Fuel Injector Solenoid Coil Test .
    • For an intermittent condition, refer to Intermittent Conditions .

Test Description

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

  1. This step verifies that the condition is present

    2.

  2. This step determines if the condition affects an entire bank of the engine. The cylinder pairings are 1, 3, 5, 7, and 2, 4, 6, 8.

    3.

  3. This step tests for voltage at the fuel injector harness connector. The fuel injector relay supplies power to the coil side of the fuel injector harness connector.

    4.

  4. This step verifies that the Alternative Fuels ECM is able to control the fuel injector. If the test lamp blinks, then the Alternative Fuels ECM and wiring are OK.

    5.

  5. This step tests if a ground is constantly being applied to the fuel injector.

    6.

  6. This step tests for voltage at the fuel injector relay coil. The IGN E fuse supplies power to the coil side of the fuel injector relay. If the fuse is open, a short to ground on the ignition supply circuit is indicated.

    7.

  7. This step tests for voltage at the fuel injector relay switch. If the fusible link is open, a short to ground on the B+ supply circuit is indicated.

    8.

  8. This step tests the ground circuit of the fuel injector relay. If the test lamp does not illuminate, repair the open circuit.

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

  1. With a scan tool clear the DTCs.
  2. Idle the engine at the normal operating temperature.
  3. With a scan tool observe the Alternative Fuels Diagnostic Trouble Code (DTC) information.

Does the scan tool indicate that any of the DTCs P0201-P0208 set this ignition?

Go to Step 4

Go to Step 3

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 Diagnostic Aids

4

Does the condition affect an entire bank of the engine?

Go to Step 10

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Disconnect the appropriate harness connector of the fuel injector.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition voltage circuit of the fuel injector with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 6

Go to Step 17

6

  1. Connect the fuel injector test lamp J 34730-2C between the control circuit and the ignition voltage circuit of the fuel injector harness connector.
  2. Start the engine.

Does the test lamp blink?

Go to Step 15

Go to Step 7

7

Does the test lamp remain illuminated at all times?

Go to Step 9

Go to Step 8

8

Test the control circuit of the fuel injector for a short to voltage or an open. 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 23

Go to Step 16

9

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

Did you find and correct the condition?

Go to Step 23

Go to Step 22

10

  1. Turn OFF the ignition.
  2. Disconnect the appropriate fuel injector relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition voltage circuit of the injector relay coil with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 11

Go to Step 18

11

Probe the battery voltage circuit of the injector relay switch with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 12

Go to Step 18

12

Probe the ground circuit of the injector relay with a test lamp connected to B+.

Does the test lamp illuminate?

Go to Step 13

Go to Step 19

13

Test the ignition feed circuit of the fuel injectors for an open between the fuel injector relay and the splice. 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 23

Go to Step 14

14

Inspect for poor connections at the harness connector of the fuel injector relay. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 23

Go to Step 20

15

Inspect for poor connections at the harness connector of the fuel injector. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

Go to Step 23

Go to Step 21

16

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

Did you find and correct the condition?

Go to Step 23

Go to Step 22

17

Repair the ignition voltage circuit of the fuel injector. Refer to Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you complete the repair?

Go to Step 23

--

18

Repair the voltage circuit of the fuel injector relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you complete the repair?

Go to Step 23

--

19

Repair the ground circuit of the fuel injector relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you complete the repair?

Go to Step 23

--

20

Replace the appropriate fuel injector relay.

Did you complete the replacement?

Go to Step 23

--

21

Replace the fuel injector. Refer to Fuel Injector Replacement .

Did you complete the replacement?

Go to Step 23

--

22

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

Did you complete the replacement?

Go to Step 23

--

23
  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 24

Go to Step 2

24

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