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DIESEL PCM, DLC, I/P
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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 PCM 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.
Diagnostic Aids
If the glow plug relay is stuck in the ON position, check for proper operation of glow plugs. When 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, 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
Number(s) below refer to the number(s) on the diagnostic table.
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This step will make sure OBD system check is performed.
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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 | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
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Important: Before clearing DTCs use the scan tool Capture Info to record freeze frame and failure records for reference, as data will be lost when Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||||||||
Is DTC:
stored as history or current codes? | -- | Go to the Applicable DTC Table | ||||||||
Do all glow plugs turn test light ON? | -- | |||||||||
Does each circuit turn the test light ON? | -- | |||||||||
5 | Does the test light stay ON all the time for each glow plug terminal (even when the glow plugs aren't commanded ON)? | -- | ||||||||
6 |
Is the test light ON for all terminals? | -- | ||||||||
7 | Repair the short to voltage on the glow plug output circuit or the short to voltage on the glow plug signal circuit. Is the action complete? | -- | -- | |||||||
8 | Replace the glow plug relay. Refer to Glow Plug Relay Replacement . Is the action complete? | -- | -- | |||||||
9 | Replace all glow plugs that do not turn ON the test light. Refer to Glow Plugs . Is action complete? | -- | -- | |||||||
10 | Repair open in each circuit that does not turn ON the test light? Is action complete? | -- | -- | |||||||
11 | Operate vehicle within the conditions under which system was noted. Does system operate properly? | -- | System OK |
