Heater Core Coolant Pump W/HP5
WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The primary purpose of the heater core coolant pump is to circulate engine coolant through the HVAC heater core when heat is required in the cabin for comfort. This normally happens when the vehicle is in an Auto Stop and the mechanical pump is not spinning. If the HVAC control module has determined heat is needed for the cabin, this pump is turned on once the engine is shut off so the customer does not notice a change in heater duct discharge temperatures. The HVAC control module controls the auxiliary cooland pump relay via the heater core coolant pump relay control circuit. Heater core coolant pump relay supplies B+ voltage to the heater core coolant pump.