Glow Plug Control

Glow plugs are used to warm the cylinders to improve cold-engine starting. The Powertrain Control Module (PCM) uses the Engine Oil Temperature (EOT) sensor and Barometric Pressure (BARO) sensor to determine how long the glow plugs will be on. The PCM energizes the glow plugs longer if the engine is very cold or if the barometric pressure is low at high altitudes.

The PCM controls the relay that supplies power to the glow plugs with the Glow Plug Control (GPC) signal. When the GPC signal is grounded by the PCM the relay closes, turning the glow plugs on.

The glow plugs are controlled by the following sequence:
1. PCM energizes the glow plugs.
2. The PCM energizes the glow plugs immediately after the ignition is placed in the ON position.
3. The PCM then determines how long glow plugs will be on with the EOT sensor and the BARO sensor. The required time to warm up the cylinder decreases the engine oil temperature and barometric pressure increases at low altitudes.