It is the Heater Auxiliary Water Pump.
From the book:
With the ignition ON, the heater auxiliary water pump runs continuously and increases the flow of coolant to the heater core. At low RPM or idle, coolant circulation to the heater core is low and a failure in this pump would result in poor passenger compartment heating. The pump is mounted on the RH strut tower.
Put your hand on the pump and wiggle the connector and see if it starts working. I had a bad connector and a bad pump. I got one from the junkyard for 15 or 20 dollars. If you do that, make sure you get a receipt. I had to go back a few times to get one that worked.