P0485
Fan Power/Ground Circuit
- Severity
- High
- Driving
- Drivable — book it in
A fault in the cooling fan's power or earth circuit. Fans draw a large current, so their supply and earth connections carry more than most - and corrosion or a loose connection there produces heat, voltage drop and a fan that turns slowly or not at all.
Possible causes
- CommonFailed fan motor
- CommonFailed fan relay or control module
- CommonBlown fuse on the fan circuit
- CommonCorroded connector or damaged wiring
- PossibleDebris jamming the fan
- PossibleCorroded earth at the fan
- RareFailed control module driver
- CommonCorroded or loose earth connection at the fan
- CommonHeat-damaged connector at the fan
What you might notice
- Engine running hot in traffic but cool at speed
- Cooling fan not running, or running constantly
- Air conditioning performance poor at low speed
- Temperature gauge climbing when stationary
- Check engine light on
What to check, in order
- Perform a voltage drop test on the fan supply and earth while the fan is running. High resistance in a corroded connection makes the fan turn slowly while everything tests as connected.
- Inspect the fan earth point for corrosion and clean it.
- Look for heat discolouration at the connector, which indicates a poor connection that has been running hot.
- Watch the temperature gauge in slow traffic and stop if it climbs. A fan fault shows itself when the car is stationary and clears at speed, because airflow through the radiator does the fan's job - that pattern is the clearest evidence available and costs nothing to observe.
- Check whether the fan runs at all when the engine is hot or the air conditioning is on.
- Check the fuse and swap the relay with an identical one from elsewhere in the box.
- Inspect the connector and the fan earth for corrosion.
- Check for debris in the fan and that it spins freely with the engine off and cool.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Auxiliary emission controls
P0400P0401P0402P0403P0404P0405P0406P0407P0408P0409P0410P0411P0412P0413P0414P0415P0416P0417P0418P0419P0420P0421P0422P0423P0424P0425P0426P0427P0428P0429P0430P0431P0432P0433P0434P0435P0436P0437P0438P0439P0440P0441P0442P0443P0444P0445P0446P0447P0448P0449P0450P0451P0452P0453P0454P0455P0456P0457P0458P0459P0460P0461P0462P0463P0464P0465P0466P0467P0468P0469P0470P0471P0472P0473P0474P0475P0476P0477P0478P0479P0480P0481P0482P0483P0484P0485P0486P0487P0488P0489P0490P0491P0492P0493P0494P0495P0496P0497P0498P0499