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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC K Sierra - 4WD (LPG) 🢒 Engine 🢒 Engine Controls - 6.0L 🢒 Fuel Injector Circuit Diagnosis

Circuit Description

The alternative fuels ECM enables the appropriate fuel injector on the intake stroke for each cylinder. Each bank of fuel injectors has a fuel injector relay. Battery voltage is supplied directly to the switch side of the fuel injector relays. An ignition voltage is supplied to the coil side of the fuel injector relays. The alternative fuels ECM controls each fuel injector by grounding the control circuit via a solid state device called a driver.

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 determines if an open IGN E fuse is causing the condition.

    2.

  2. This step tests for a short to ground on the ignition voltage supply circuit of the fuel injector relay.

    3.

  3. This step determines if one of the fuel injector relays is causing the condition. If the IGN E fuse opens when a fuel injector relay is installed, replace the relay.

    4.

  4. This step determines the AF fuel pump relay is causing the condition. If the IGN E fuse opens when the AF fuel pump relay is installed, replace the relay.

    5.

  5. This step determines the Alternative Fuels ECM is causing the condition. If the IGN E fuse opens when the harness connector of the Alternative Fuels ECM is installed, replace the Alternative Fuels ECM.

    6.

  6. This step tests the ignition voltage circuit of the fuel injector relays.

    7.

  7. This step tests the battery voltage circuit of the fuel injector relays.

    8.

  8. This step tests the battery voltage circuit of the fuel injector relays for a short to ground. If the test lamp illuminates, repair the short to ground, and replace the fusible link.

    9.

  9. This step tests the battery voltage circuit of the fuel injectors for a short to ground between the fuel injector relay and the fuel injectors. If the test lamp illuminates, repair the short to ground, and replace the fusible link.

    10.

  10. This step tests the fuel injector relays. If the test lamp does not illuminate, inspect the appropriate relay for proper terminal connections.

Step

Action

Values

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, observe the alternative fuels ECM diagnostic trouble code (DTC) information.

Are DTCs P0201-P0208, or DTC P1650 set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

Important: Verify that there is adequate CNG fuel in the fuel tank before proceeding with this diagnostic.

Crank the engine for the specified amount of time.

Does the engine start and idle on all cylinders?

4 seconds

Go to Diagnostic Aids

Go to Step 4

4

Inspect the IGN E fuse.

Is the IGN E fuse open?

--

Go to Step 5

Go to Step 9

5

  1. Turn OFF the ignition.
  2. Disconnect both fuel injector relays.
  3. Disconnect the alternative fuels fuel pump relay.
  4. Disconnect the alternative fuels ECM harness connector C001. Refer to Alternative Fuels Engine Control Module Replacement .
  5. Probe the ignition voltage circuit of the fuel injector relays, at the under-hood bussed electrical center, with a test lamp connected to B+.

Is the test lamp illuminated?

--

Go to Step 17

Go to Step 6

6

  1. Install a new IGN E fuse.
  2. Turn ON the ignition, with the engine OFF.
  3. Install the fuel injector relays one at a time.
  4. Inspect the IGN E fuse after each relay is installed.

Does the fuse open after either relay is installed?

--

Go to Step 22

Go to Step 7

7

  1. Install the AF fuel pump relay.
  2. Inspect the IGN E fuse.

Is the fuse open?

--

Go to Step 23

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Install the alternative fuels ECM harness connector C001.
  3. Turn ON the ignition, with the engine OFF.
  4. Inspect the IGN E fuse.

Is the fuse open?

--

Go to Step 24

Go to Diagnostic Aids

9
  1. Turn OFF the ignition.
  2. Disconnect both fuel injector relays.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition voltage circuit of both fuel injector relays with a test lamp connected to a known good ground.

Does the test lamp illuminate for both circuits?

--

Go to Step 10

Go to Step 16

10

Probe the battery voltage circuit of both fuel injector relays with a test lamp connected to a known good ground.

Does the test lamp illuminate for both circuits?

--

Go to Step 13

Go to Step 11

11

Probe the battery voltage circuit of the circuit that did not illuminate the test lamp with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 18

Go to Step 12

12

Probe the battery voltage circuit of the fuel injectors, at the fuel injector relay, with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 19

Go to Step 21

13

Probe the ground circuit of both fuel injector relays with a test lamp connected to B+.

Does the test lamp illuminate for both circuits?

--

Go to Step 14

Go to Step 20

14
  1. Turn OFF the ignition.
  2. Install both fuel injector relays.
  3. Disconnect a harness connector of a fuel injector from each bank of the engine.
  4. Turn ON the ignition, with the engine OFF.
  5. Probe the battery voltage circuit of the fuel injectors with a test lamp connected to a known good ground.

Does the test lamp illuminate for both circuits?

--

Go to Diagnostic Aids

Go to Step 15

15

Inspect for proper terminal contact at the harness connector of the appropriate fuel injector relay. 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 25

Go to Step 22

16

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

Did you complete the repair?

--

Go to Step 25

--

17

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

Did you complete the repair?

--

Go to Step 25

--

18

Important: Replace the appropriate fusible link after the short to ground is repaired.

Repair the short to ground in the battery voltage circuit of the fuel injector relay. Refer to Circuit Testing in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

19

Important: Replace the appropriate fusible link after the short to ground is repaired.

Repair the short to ground in the battery voltage circuit between the fuel injector relay and the fuel injectors. Refer to Circuit Testing in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

20

Repair the ground circuit of the fuel injector relays for an open. Refer to Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you complete the repair?

--

Go to Step 25

--

21

Repair the battery voltage circuit of the fuel injector relays for an open. Refer to Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you complete the repair?

--

Go to Step 25

--

22

Replace the appropriate fuel injector relay.

Did you complete the replacement?

--

Go to Step 25

--

23

Replace the AF fuel pump relay.

Did you complete the replacement?

--

Go to Step 25

--

24

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

Did you complete the replacement?

--

Go to Step 25

--

25

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2