The ground path is provided at G104.ĭuring low speed operation, the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block. The relays are arranged in a series parallel (S/P) configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The engine cooling fan system consists of 2 puller type electrical cooling fans and 3 fan relays. You must have a cooling system problem of some sort !ĭo the cooling fans come on when A/C is switched on ? Fan's should come on ! Does your vehicle have two or three cooling fan's ? The result is a parallel circuit with both fans running at high speed.Īre the radiator fans coming on ? You mite take it an have it checked for DTC'S - diagnostic trouble code's. During high speed fan operation, both engine cooling fans have there own ground path. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 maxifuse?® on the cooling fan motor supply voltage circuit to the right cooling fan. This energizes the cooling fan relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. After a 3 second delay, the PCM/ECM supplies a ground path for the cooling fan 2 relay and the cooling fan relay through the high speed cooling fan relay control circuit. The result is a series circuit with both fans running at low speed.ĭuring high speed operation, the PCM/ECM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. The ground path for the left cooling fan is through the cooling fan relay and the right cooling fan. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool fan 1 maxifuse?® through the cooling fan motor supply voltage circuit to the left cooling fan.

The ground path is provided at G100.ĭuring low speed operation, the PCM/ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. The cooling fans and fan relays receive battery positive voltage from the underhood junction block. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) or engine control module (ECM) to operate both fans together at low or high speeds. The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. Refer to Cooling System Description and Operation It means you should take your vehicle to a qualified repair shop, at least that's the car makers thought.

E37 ecm pinout