Engine bay cooling fan

When the engine coolant temperature falls below 96 °C (205 °F), the ECM disconnects the earth of the cooling fan relay coil and the cooling fan motor is switched off.

Engine bay cooling fan

The ambient air temperature sensor (C0884) provides an input to the ECM (C0159) on a SW wire. The earth side of the ambient air temperature sensor (C0884) is connected to the ECM (C0159) by a KB wire.

If an engine compartment temperature of approximately 85 °C (185 °F) is reached, the ECM earths the NB wire connected between the coil of the engine bay cooling fan relay (C1448) and the ECM (C0159). The engine bay cooling fan relay (C1448) energises and supplies power to the engine bay cooling fan motor (C1328) on a NY wire. The engine bay cooling fan motor (C1328) is earthed by a B wire connected to an earth header (C0550), and operates to boost the air flow through the engine compartment.

If the engine compartment temperature reaches approximately 130 °C (266 °F) the ECM earths the GR wire, between the instrument pack (C0234) and the ECM (C0159), to illuminate the engine bay fan warning lamp.

When the engine compartment temperature decreases below 110 °C (230 °F), the engine bay fan warning lamp is extinguished. The engine bay cooling fan motor is switched off 1 minute after the engine compartment temperature decreases to 75 °C (167 °F), or immediately the temperature decreases below 60 °C (140 °F).

NOTE: It is normal for the engine bay cooling fan motor to run for up to 8 minutes after the ignition has been switched off.

If the warning lamp is illuminated and the engine bay cooling fan motor runs continuously when the ignition switch is in position II, the probable cause is a faulty ambient air temperature sensor.