Circuit Description
Important: This check only applies to the Federal Glow Plug System. The Federal Glow Plug System does not have the ability to detect for a glow plug failure. The California Glow Plug System can determine glow plug failure by setting a DTC P0380.
The glow plug system helps provide the heat required to begin combustion when starting the engine at cold ambient temperatures. The glow plugs are heated before and during cranking, as well as during the initial engine operation. The powertrain control module (PCM) controls the amount of time the glow plugs are energized by monitoring coolant temperatures and the glow plug voltage. This system check will check the glow plugs and the glow plug feed circuit coming from the relay.
Diagnostic Aids
If the glow plug relay is stuck in the ON position, check for proper operation of glow plugs. When the glow plugs are commanded ON by the scan tool, an internal PCM 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, note if 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 ensure that the OBD system check is performed.
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This step ensures that there are no other DTCs stored that will affect the operation of the glow plug system.
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This step checks each glow plug for an open.
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This step checks each glow plug feed circuit for an open.
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||||||||
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Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame/Failure Records for reference. The data in the control module is deleted once the Clear Info function is used. Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | ||||||||
Verify whether any of the following DTCs are stored as history or current codes:
Are any of the above DTCs stored as history or current codes? | Go to Step 3 | ||||||||
Do all of the 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 stay ON 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 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 . Did you complete the replacement? | Go to Step 11 | -- | ||||||
9 | Replace all of the glow plugs that do not turn the test light ON. Refer to Glow Plug Relay Replacement . Did you complete the replacement? | Go to Step 11 | -- | ||||||
10 | Repair the open in each circuit that does not turn the test light ON. Did you complete the repair? | Go to Step 11 | -- | ||||||
11 | Operate the vehicle within the conditions under which system was noted. Does the system operate properly? | System OK | Go to Step 1 | ||||||
