Glow Plug System: Description and Operation

GLOW PLUG SYSTEM

Glow Plug Control Module:

The 6.4L diesel engine uses a glow plug system that preheats air in the combustion chamber to improve cold engine starting.

The system consists of the following components:
- Glow plug wire harness (one per bank)
- Glow plugs
- Glow plug control module
- PCM
- Engine coolant temperature (ECT) sensor
- Barometric pressure (BARO) sensor

The glow plug monitor system is part of the On-Board Diagnostics II (OBD II) System.

The glow plug system is electronically controlled by the PCM. If the oil temperature is below 55°C (131°F), the PCM will energize the glow plugs immediately after the key is placed in the ON position. Then, depending on the readings from the engine coolant temperature (ECT) sensor and the BARO sensor, the PCM determines how long the glow plugs will be on. Glow plugs are always turned on for a predetermined period of time, except when ECT is 65.6°C (150°F) or above and BARO is above the 78kPa (11.3 psi). If these conditions are met, the PCM will bulb check the wait-to-start lamp but not energize the glow plug module. The BARO sensor is internal to the PCM.

Glow Plugs - PCM-Controlled:

The glow plugs are located in the cylinder heads, under the glow plug wiring harnesses on either bank.

The glow plug ON time varies from 0-120 seconds depending on battery voltage, ECT and BARO.

The glow plug ON time is independent of the WAIT-TO-START lamp ON time.

The glow plug control module (GPCM) system is designed to find failed glow plugs or failed wiring in the glow plug system.