In the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Eight glow plugs are used as an aid to starting.

Control of the glow plugs has been accomplished by moving the logic for controlling the heat of the plugs to the powertrain control module (PCM). The new logic can incorporate the higher accuracy of digital processing compared to the previous analog controller. Additionally, logic involving engine speed and estimates of engine combustion can be added to the traditional time and temperature data used in the previous controller. This capability yields more optimum heat times for the glow plugs, thus pre-glow times can be kept to a minimum for short wait to crank times and maximum glow plug durability.

A normal functioning system operates as follows:

The glow plug initial ON times may range from 1 to 16 seconds and cycling ON/OFF times vary also with system voltage and/or temperature. Lower temperature causes longer duration of cycling.

The PCM provides glow plug operation after starting a cold engine. This after glow operation is initiated when the ignition switch is returned to Run, from the Start position. This function helps clean up excessive white smoke and/or poor idle quality after starting.

These are 6-volt heaters (operated at 12 volts) that turn ON, when the ignition switch is turned to the run position, prior to starting the engine. They remain pulsing a short time after starting, then are turned OFF.

A Wait to Start lamp on the instrument panel, provides information on engine starting conditions. The Wait to Start lamp will not come ON during post glows.

The glow plug relay is mounted at the rear of the left cylinder head. The glow plug relay is a solid state device which operates the glow plugs.

The PCM uses a ignition voltage signal to control the solid state circuitry of the glow plug relay.