Q: How to troubleshoot and replace the engine cooling fan on a Toyota Prius?
A: The Cooling Fan Assembly on these models is controlled by the PCM through inputs from the Coolant Temperature Sensor. To test an inoperative fan motor, check the fuses and the relay in the engine compartment fuse and relay box before proceeding with further tests. If the motor still doesn't work, use fused jumper wires to connect it directly to a 12-volt battery. If the motor tests okay but is still inoperative, the fault may lie in the relays, fuse wiring, or PCM. Replacement procedures vary by model year but generally involve draining coolant, removing the radiator support, disconnecting hoses and wiring, and lifting out the fan motor assembly. Installation is the reverse of removal, and the air conditioning system should be recharged at a repair shop.