Faulty Glow Plug
Glow Plug harness is open or shorted
Glow Plug circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
The engine may be harder to start
The glow plug system is used to assist in providing the heat required to begin combustion during cold engine temperatures. The glow plugs are heated before and during cranking, as well as initial engine operation. The Engine Control Module (ECM) controls the glow plug ON times by monitoring coolant temperature and glow plug voltage. The California Glow Plug system has eight individual glow plug supply circuits between the controller and the glow plugs. If the feedback voltage from the controller to the ECM is not within range, DTC P0380 will set.