P0485: Fan Power/Ground Circuit

P0485 monitors the supply or ground path of the fan or its control module – not the control line. It is typical of fans with their own module (PWM or LIN), which can report undervoltage or a missing ground. The high currents involved, often 20–60 A, make contact resistance at ground and supply connections and fuse holders the main cause. No manufacturer table available to us lists P0485, so thresholds and warning-lamp behaviour remain open; CARB requires output components to be monitored. The fan then runs intermittently or not at all.

Symptoms

• Warning lamp (depending on the maker)
• Fan does not run or only intermittently
• Overheating at standstill, weak air conditioning
• Possibly burnt smell or discoloured connector

Most likely causes

• Fan or fan module ground loose, corroded or broken
• Fan fuse blown or fuse holder overheated or corroded
• Relay power contact burnt – voltage drop under load
• Connector at the fan scorched, water ingress
• Fan control module faulty

What to check, in order

Start with the simplest. You can tick off each step.

1. With the engine cold, check the coolant level; never do this when the system is hot
2. Check the actual temperature in live data
3. Make sure the fan comes on when it should
4. Check the thermostat and connector
5. Measure the sensor and replace it if its readings do not make sense

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P0485 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 4: Emissions
• 85: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0485?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P0485?

The most common causes are: fan or fan module ground loose, corroded or broken; fan fuse blown or fuse holder overheated or corroded; relay power contact burnt – voltage drop under load.

Related codes

• P0484Fan Circuit Current High
• P0480Fan 1 Control Circuit
• P0481Fan 2 Control Circuit
• P0483Fan Rationality Check
• P0691Fan 1 Control Circuit Low
• P0693Fan 2 Control Circuit Low

Sources

• law.cornell.edu: 13 CCR 1968.2
• saabwisonline.com: dtc p0480 p0482 or p0691 p0696
• patents.google.com: US6016965

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.