Glow plug relay (Engine management system - EDC)

Glow plug relay

When the starter switch is turned to position ’II’ the ECM energises the glow plug relay and illuminates the glow plug warning light in the fascia. The glow plug relay supplies a current from the battery to the 4 glow plugs to assist cold starting by raising the temperature of the compressed air in the cylinder to ignition point.

Glow plug

The length of time the glow plugs will remain operational is dependent upon the initial engine temperature determined by the ECM from the coolant temperature sensor. Once the glow plugs have operated for their pre-determined time the control unit will remove the supply from the glow plug relay and extinguish the glow plug warning light on the fascia.

If an attempt to start the engine is made before the glow plugs have finished operating the ECM will remove the supply from the glow plug relay, switching off the glow plugs.

TestBook connector

The TestBook connector is located forward of the centre console on the RH side. The TestBook connector is provided to enable diagnosis via TestBook to be carried out without disturbing the system electrical connections and to allow the ECM’s ability to store certain faults to be utilised.

Engine warning light

The ECM has a built in self-diagnosis function. If a fault is detected the engine warning light, in the instrument pack, will illuminate and the ECM will implement a back-up facility to enable the system to continue functioning, though at a reduced level of performance. If a serious fault is detected the warning light will illuminate and the engine management system will shut down preventing the car from being started.

The warning light will remain illuminated until the starter switch is turned off. If the fault is still present when the starter switch is turned back on the warning light will illuminate. If the fault is not present when the starter switch is turned on, the warning light will remain extinguished, but a fault code will be stored in the ECM’s memory.