Why is my battery cooling system not working?

A description of the system and fault code indicated a problem with the cooling fan control circuit responsible for cooling the high voltage (HV) battery. Understanding the operation of the system is essential when diagnosing recorded faults; after all, how can we diagnose components if we don’t know how they function?

How does the cooling system work on a battery?

A command signal from the HCU is delivered to the cooling fan to increase or decrease fan speed, depending on battery temperature. A feedback signal from the cooling fan is sent to the Battery Control Module (BCM), where this value is converted into serial data and returned to the HCU, completing the loop.

What happens to the ECU when the battery is disconnected?

When the vehicle’s battery is disconnected, some ECUs will lose information stored in their memory. In some cases, this may also occur if the battery voltage becomes low or if the battery is recharged. After the battery is reconnected, these systems must be initialized before they can work properly.

Can a 12 V battery be cooled by a cooling fan?

Testing the cooling fan circuit required the 12 V battery to be reconnected and the ignition switched on, with the hybrid system still isolated. This is normal procedure and generated additional DTCs (which were erased on completion of the repair). Note: Switching the ignition on with the HV Service Plug removed does not activate the HV system.

When do you know you have a cooling system problem?

When the engine starts to get above the normal operating temperature, watch the cooling fan. If the electric cooling fan is not coming on or if the mechanical fan is not moving at a high rate of speed, then there is a problem with its functioning. If you have a mechanical fan that is not functioning, the fan clutch must be replaced.