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Home >> GMC >> 2001 >> C3500 HD 6.5 F, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 6.5L - Troubleshooting >> Glow Plug System Diagnosis >> Test Description
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Test Description

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

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

Step Action Yes No
1 
IMPORTANT: Before clearing DTCs use the scan tool Capture Info to record Freeze Frame/Failure Records for reference, as data will be lost when Clear Info function is used.
Did you perform the Diagnostic System Check-Engine Controls?		 Go to Step 2  Go to Diagnostic System Check - Engine Controls
2  Is DTC PO117, PO118, or PO380 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 B+, 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. With a test lamp, jumper each glow plug connector terminal to ground.
  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 stay illuminated all the time for each glow plug terminal (even when the glow plugs aren't commanded ON)? Go to Step 6  Go to Step 11 
6
  1. Disconnect the glow plug output (gray) cable from the glow plug relay.
  2. Probe each glow plug terminal with a test lamp connected to ground.
Is the test lamp illuminated for all terminals?		 Go to Step 7  Go to Step 8 
7 Repair the short to voltage on the glow plug output circuit or the short to voltage on the glow plug signal circuit.
Did you complete the repair?		 Go to Step 11  -
8 Replace the glow plug relay. Refer to Glow Plug Relay Replacement (Federal) or Glow Plug Relay Replacement (California) .
Did you complete the replacement?		 Go to Step 11  -
9 Replace all glow plugs that do not illuminate 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 illuminate the test lamp?
Did you complete the repair?		 Go to Step 11  -
11 Operate vehicle within the conditions under which problem was noted.
Does system operate properly?		 System OK Go to Step 1 
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