California Models

PURPOSE
The 7.3L Direct Injection (DI) diesel engine uses a glow plug system which preheats air in the combustion chamber to improve cold engine starting.

OPERATION
The glow plug system is electronically controlled by the powertrain control module. The Powertrain Control Module (PCM) energizes the glow plugs immediately after the key is placed in the ON position and then determines how long the glow plugs will be on according to the engine oil temperature and the barometric pressure. The required time for the glow plugs to be energized decreases as the engine oil temperature and barometric pressure increase.

NOTES
- The glow plugs are self-regulating, and the PCM controls relay ON time.
- The PCM protects the glow plugs by energizing them for short durations if the battery voltage is abnormally high.
- The system incorporates a shunt and extra wiring for the On-Board Diagnostic II (OBD II) system. The shunt is added to the glow plug relay to register voltage to both the left and right bank glow plugs.
- Three sensor wires are added to the relay to sense failures in the system.

COMPONENTS
The system consists of eight glow plugs, the glow plug relay, PCM, Engine Oil Temperature (EOT) sensor and Barometric Pressure (BARO) sensor.