Auxiliary Water Pump: Description and Operation

An electric auxiliary water pump is used on all models to aid in circulating the engine coolant through the front and rear heater core (depending on application). The auxiliary water pump is mounted to the right front frame rail by a rubber isolator (1) and consists of a molded plastic housing (2) with two heater hose connections (3), a 12 volt direct current (DC) motor and impeller assembly (4) with an integral wire connector receptacle (5).

The A/C-heater control operates the auxiliary water pump when all of the following conditions have been met.
- Vehicle speed below 48 km/h (30 mph)
- Coolant temperature between 10° C (50° F) and 110° C (230° F)
- Front blower motor turned On
- Rear temperature heat setting above the halfway setting (60% heat)
- No fault conditions detected

The A/C-heater control turns the auxiliary water pump Off when any of the following conditions occur.
- Vehicle speed above 48 km/h (30 mph)
- Coolant temperature above 110° C (230° F)
- Front blower motor turned Off

The auxiliary water pump cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The auxiliary water pump is diagnosed using a scan tool.