Code P0480, radiator fans will not turn on?

GOCUSSJ5

MEMBER
2010 GMC SIERRA
4.8L
V8
2WD
AUTOMATIC
250,000 MILES

Hello!

I am having an issue with my truck listed above. The radiator fans will not kick on and I got an error code P0480. If I did disconnect the cooling sensor they will kick on and will not turn off until I plug it back in. I’ve replaced the cooling sensor, module and today I took apart the harness to follow the wires from the cooling sensor to the computer. It’s not cute so I am just 100% lost on what it could be. Some say it’s the computer that’s gone bad, but my situation seems a bit unique. Any help would be amazing.

1 Reply

BORIS K

MECHANIC
795 POSTS

Hello,

P0480 - Cooling Fan 1 Control Circuit

Possible Causes of the Code P0480
Faulty Cooling Fan 1 Relay
Cooling Fan 1 Relay harness is open or shorted
Cooling Fan 1 Relay circuit poor electrical connection
Faulty Cooling Fan 1
Faulty Cooling Fan Control Module
Faulty Engine Control Module (ECM)

The scenario when you unplug the engine coolant temperature sensor (ECT) and the cooling fan runs is normal behavior. It is a fail safe from the engine ECM in case of ECT sensor failure

Below please see cooling fan activation wiring diagram from the ECM to the under-hood fuse block

Suggest checking the wiring back from the ECM to the under-hood fuse block. Possibly swap/replace relays.

How to test wiring:
https://www.2carpros.com/articles/how-to-check-wiring

How to test relay:
https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Cheers, Boris

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