What does it mean?
P1625 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cooling Fan Relay High Circuit Malfunction .
Symptoms
- MIL (check engine lamp) on
- Cooling fan running constantly, sometimes even with the ignition off, flattening the battery
- Or the fan never running, with the engine overheating in slow traffic
- Air conditioning cooling poorly at a standstill
- Coolant temperature climbing in traffic and falling again once moving
- A fan fuse that blows repeatedly, or a burning smell from the relay box
Likely causes
- Fan relay control circuit shorted to battery positive, or open
- Failed relay with welded, burnt or high-resistance contacts
- Corroded relay socket or spread terminals in the fuse and relay box
- Chafed wiring between the relay box, the module and the fan motor
- Fan motor drawing excessive current from worn brushes or a seized bearing, burning the relay
- Poor ground at the fan motor or the module
- Module output driver damaged by the fault in the circuit
How to fix it
- Note first whether the fan is stuck on or never runs; that single observation splits the diagnosis
- Command the fan with the scan tool and watch what happens at the relay and the motor
- Fit a known-good identical relay as a quick test and inspect the socket for heat discolouration and melted plastic
- With the relay removed, check the control circuit for voltage present when it should be off, and for continuity back to the module
- Measure the fan motor current draw and confirm the motor spins freely by hand with the battery disconnected
- Voltage-drop test the fan and module grounds
- Repair the wiring or replace the relay or fan motor as the tests indicate, then verify normal fan staging through a full warm-up