What does it mean?
P1479 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: A/T Fan Relay Circuit Malfunction .
Symptoms
- MIL on
- Transmission fluid temperature rises, especially when towing or crawling in traffic
- The fan does not run when it is commanded on
- Transmission may enter a protection strategy with firmer or restricted shifting
- Coolant temperature can climb as well when the same fan serves the radiator
Likely causes
- Failed transmission cooling fan relay with an open coil or burnt contacts
- Corroded, loose or heat-damaged terminals in the relay socket
- Open or shorted control wire between the module and the relay coil
- Blown fuse or fusible link in the fan power feed
- Seizing fan motor drawing excessive current and destroying the relay contacts
- Poor ground for the relay or the fan motor
- Module output driver failure
How to fix it
- Monitor transmission fluid temperature and the commanded fan state with a scan tool
- Inspect the relay socket for melted plastic, discoloured terminals and spread contacts
- Substitute a known good identical relay and see whether the fan responds
- Verify feed voltage at the relay and continuity of the control wire back to the module
- Measure fan motor current draw; a high reading points to a failing motor
- Repair the wiring, or replace the relay or fan motor as indicated by the tests
- Confirm the fan runs and fluid temperature stabilises after the repair