P0485: Cooling Fan Power/Ground Circuit
What to do
Watch the temperature gauge in traffic. A fan running slowly on a poor earth still moves some air, so the car may cope at speed and overheat when stationary. Overheating is expensive; do not sit in a queue with a rising gauge.
What this code means
A fault in the fan's power supply or its ground rather than in the control signal. The fans draw a large current, so their supply and earth connections are heavy and are usually bolted rather than plugged — and a corroded earth bolt on the body or subframe is a classic cause, particularly on older vehicles and in regions that salt the roads.
A poor earth produces a fan that runs slowly rather than not at all, which cools inadequately without ever appearing to be broken. Measuring the voltage drop across the earth connection while the fan runs finds it in seconds and is far more revealing than a resistance check with the circuit off.
Likely causes
Start here
- Corroded earth connection · moderate
- Blown cooling fan fuse · easy
- Corroded or loose connector · easy
- Road damage to underfloor wiring · moderate
Less common
- Failed cooling fan relay · easy
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
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