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

  1. 2:  This step will make sure there are no other DTCs stored that will affect the operation of the glow plug system.
  2. 3:  This step will check each glow plug for an open.
  3. 4:  This step will check each glow plug feed circuit for an open.
Glow Plug System Diagnosis

Step Action 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  Are DTCs P0117, P0118, P0380 stored as history or current codes? Go to Diagnostic Trouble Code (DTC) List Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect all the glow plugs.
  3. With a test lamp connected to battery voltage, probe the spade terminal on each glow plug.
Do all glow plugs illuminate the test lamp?		 Go to Step 4  Go to Step 9 
4 
  1. Turn ON the ignition, with the engine OFF.
  2. Verify the glow plugs are still disconnected.
  3. Probe each glow plug supply voltage circuit with a test lamp connected to ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
  4. With a scan tool, command the glow plugs ON.
Does each circuit illuminate the test lamp?		 Go to Step 5  Go to Step 10 
5 Does the test lamp illuminate all the time for each glow plug terminal, even when the glow plugs are not commanded ON? Go to Step 6  Go to Step 11 
6
  1. Disconnect the glow plug supply voltage connection from the glow plug relay.
  2. Probe each glow plug terminal with a test lamp connected to ground.
Does the test lamp illuminate for all terminals?		 Go to Step 7  Go to Step 8 
7 Repair the short to voltage on the glow plug supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 11  -
8 Replace the glow plug relay/controller. Refer to Glow Plug Relay Replacement (Federal Emissions) or Glow Plug Relay Replacement (California Emissions) .
Did you complete the replacement?		 Go to Step 11  -
9 Replace all glow plugs that do not turn ON the test lamp. Refer to Glow Plug Replacement - Bank 1 or Glow Plug Replacement - Bank 2 .
Did you complete the replacement?		 Go to Step 11  -
10 Repair open in each circuit that does not turn ON the test lamp. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 11  -
11 Operate vehicle within the conditions under which system fault was noted.
Does the system operate properly?		 System OK Go to Step 1 
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