Circuit Description
The glow plug system is used to assist in providing the heat required to begin combustion during engine starting at cold ambient temperatures. The glow plugs are heated before and during cranking, as well as during the engine operation. The engine control module (ECM) controls the glow plug ON times by monitoring coolant temperatures and glow plug voltage. This system check will check the glow plugs and the glow plug feed circuit coming from the relay/controller.
Diagnostic Aids
If the glow plug relay or controller is stuck in the ON position, check for proper operation of the glow plugs. When the glow plugs are commanded ON by the scan tool, an internal engine control module (ECM) timer protects the glow plugs from damage by cycling them ON for 3 seconds and then OFF for 12 seconds. Most glow plug system failures are covered by DTC P0380. If no DTCs are stored, the vehicle is hard to start and white smoke is present during cranking or after the vehicle is started, the most likely cause of failure is the glow plugs.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step will make sure there are no other DTCs stored that will affect the operation of the glow plug system.
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This step will check each glow plug for an open.
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This step will check each glow plug feed circuit for an open.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
Are DTCs P0117, P0118, P0380 stored as history or current codes? | Go to Step 3 | ||
Do all glow plugs illuminate the test lamp? | Go to Step 4 | Go to Step 9 | |
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 |
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 . 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 |
