Glow Plug System: Testing and Inspection

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

Steps 1-11:

The numbers below refer to the step numbers on the diagnostic table.
1. This step will ensure that the OBD system check is performed.
2. This step ensures that there are no other DTCs stored that will affect the operation of the glow plug system.
3. This step checks each glow plug for an open.
4. This step checks each glow plug feed circuit for an open.