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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1001 (Engine Controls - 6.6L (LLY) (Troubleshooting & Diagnosis)) >> Troubleshooting >> Malfunction Indicator Lamp (MIL) Inoperative >> Test Description

Test Description

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

The number below refers to the step number on the diagnostic table.

  1. 4:  This step tests for a short to voltage on the MIL control circuit. With the fuse removed there should be no voltage on the MIL control circuit.
Malfunction Indicator Lamp (MIL) Inoperative

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module (ECM) Connector End Views  or  Engine Controls Connector End Views 
1 Did you perform the Diagnostic System Check - Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Verify whether the instrument cluster is operational. If the instrument panel (I/P) is completely inoperative, refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gages and Console.
  2. Command the malfunction indicator lamp (MIL) ON and OFF with a scan tool.
Does the MIL turn ON and OFF when commanded with a scan tool?		 - Go to Intermittent Conditions  Go to Step 3 
3 Inspect the fuse that supplies battery voltage to the cluster.
Is the fuse open?		 - Go to Step 10  Go to Step 4 
4 
  1. Turn OFF the ignition.
  2. Remove the fuse that supplies battery voltage to the cluster.
  3. Disconnect the engine control module (ECM).
  4. Turn ON the ignition with the engine OFF.
  5. Measure the voltage from the MIL control circuit in the ECM harness connector to a good ground.
Is the voltage less than the specified value?		 1 V Go to Step 5  Go to Step 11 
5
  1. Turn OFF the ignition.
  2. Install the fuse that supplies battery voltage to the cluster.
  3. Turn ON the ignition with the engine OFF.
  4. Connect a 3-amp fused jumper wire between the MIL control circuit in the ECM harness connector and a good ground.
Is the MIL illuminated?		 - Go to Step 9  Go to Step 6 
6
  1. Turn OFF the ignition.
  2. Remove the instrument panel cluster (IPC). Refer to Instrument Panel (I/P) Assembly Replacement in Instrument Panel, Gages, and Console.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery voltage circuit of the IPC harness connector with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 7  Go to Step 12 
7 Test the MIL control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct a condition?		 - Go to Step 15  Go to Step 8 
8 Test for an intermittent and for a poor connection at the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 13 
9 Test for an intermittent and for a poor connection at the ECM. Refer to Refer to Testing for Intermittent Conditions and Poor Connections andConnector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 14 
10 Test all circuits and components that are supplied by this fuse for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Intermittent Conditions 
11 Repair the short to voltage in the MIL control circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 15  -
12 Repair the open or the short to ground in the battery voltage circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 15  -
13 Replace the IPC. Refer to Instrument Panel (I/P) Assembly Replacement in Instrument Panel, Gages and Console.
Did you complete the replacement?		 - Go to Step 15  -
14 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 15  -
15
  1. Turn OFF the ignition for 30 seconds.
  2. Start the engine.
Does the MIL operate correctly?		 - Go to Step 16  Go to Step 2 
16 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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