Engine (Coolant) Temperature Sensor

On E46, sensor is located on rear left side of engine, under exhaust manifold. On all other models, sensor is located on top front of cylinder head, behind radiator hose. This component supplies coolant temperature information to PCM. The PCM then determines whether current operating condition is at cold or normal operating temperature. During cold operating conditions, air/fuel mixture is enriched by widening fuel injector pulse width. Extra rich conditions are maintained until normal operating temperature is reached.