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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1144 (Engine Controls Diagnosis - 6.0L - Alternative Fuels (DTC P0005-DTC P2665)) >> Diagnosis >> DTC P1021, P1022, P1023, P1024, P1025, P1026, P1027, P1028: Auxiliary Injector Control Circuit >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  The engine must Crank or Run on CNG in order for this DTC to test.
  2. 4:  This step verifies that the FICM is able to control the fuel injector. Bi-fuel (KL6) equipped vehicles must be operating on alternative fuel prior to pulsing the CNG fuel injector.
  3. 5:  This step tests if a ground is constantly being applied to the fuel injector.
  4. 10:  A short to ground of the CNG injector B+ circuit will open the inline fuse and cause an entire cylinder bank to set DTCs. Test the CNG injector B+ circuits, bank injector monitor circuit, and the FICM for a shorted condition whenever the inline fuse has opened.
DTC P1021-P1028

Step Action Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Controls Connector End Views  or  Fuel Injection Control Module Connector End Views 
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. Clear the DTC information with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Crank and attempt to start the engine.
  4. Observe the DTC information with a scan tool.
Do any of the DTCs P1021-P1028 fail this ignition?		 Go to Step 3  Go to Diagnostic Aids
3
  1. Turn OFF the ignition.
  2. Disconnect the appropriate compressed natural gas (CNG) fuel injector.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the B+ circuit of the CNG fuel injector with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 Go to Step 4  Go to Step 10 
4 
  1. Probe the control circuit of the CNG fuel injector with a test lamp connected to B+.
  2. Turn OFF the ignition for 30 seconds.
    3. IMPORTANT: To ensure the fuel mode command is ALT fuel on KL6 equipped vehicles do not crank or start the engine.
  3. Turn ON the ignition, with the engine OFF.
  4. Perform the fuel injector balance test on the appropriate CNG fuel injector with a scan tool. Refer to Fuel Injector Balance Test with Tech 2 .
  5. While observing the test lamp pulse the appropriate CNG fuel injector.
Does the test lamp blink while the injector is pulsed?		 Go to Step 8  Go to Step 5 
5  Does the test lamp remain continuously illuminated? Go to Step 7  Go to Step 6 
6 Test the CNG fuel injector control circuit for an open or a short to voltage. 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 13  Go to Step 9 
7 Test the CNG fuel injector control 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 13  Go to Step 12 
8 Test for an intermittent and for a poor connection at the CNG 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 13  Go to Step 11 
9 Test for an intermittent and for a poor connection at the fuel injector control module (FICM). 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 13  Go to Step 12 
10  Repair the open or short to ground on the B+ voltage circuit of the fuel injector. 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 13  -
11 Replace the CNG fuel injector. Refer to Fuel Injector Replacement .
Did you complete the replacement?		 Go to Step 13  -
12 Replace the FICM. Refer to Fuel Injection Control Module Replacement .
Did you complete the replacement?		 Go to Step 13  -
13
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 Go to Step 2  Go to Step 14 
14 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 Go to Diagnostic Trouble Code (DTC) List System OK
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