Glow Plug System: Description and Operation

The heating of the Glow Plugs is controlled by the Glow Plug Relay in the Glow Plug Controller. Battery voltage is supplied to the relay contacts through the RED (2) wire from Junction Block. The relay is operated by a Solid-State Controller. The Controller responds to engine temperature and also to an Ignition Switch Start Input.

When the Ignition Switch is turned to RUN, battery voltage is supplied to the Enable Input of the Controller. The Glow Plug Relay within the Controller will be energized for approximately 5 seconds during which it applies voltage to the Glow Plugs and WAIT Indicator. After the initial time period the relay will be de-energized for 5 seconds then will cycle ON/OFF for approximately 10 seconds.

When the Glow Plug Controller receives the Start Input, the Glow Plugs and WAIT Indicator will cycle ON/OFF after the Ignition Switch is returned to RUN.

After approximately 25 seconds the Controller will open the Glow Plug Relay and the heating of the plugs stops. If the engine is restarted while the engine is at normal operating temperature, the Powertrain Control Module (PCM) will keep the relay contacts open so that no plug heating takes place.