Fault code P0485 – a step-by-step guide to diagnosing and fixing it

Error code P0485 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected a fault in the cooling fan control circuit. This DTC P0485 indicates problems with the electrical control of the cooling fan, which can lead to insufficient engine cooling. Specific variations in the fan control can occur with different manufacturers.

What can cause this error code?

• Defective radiator fan relay
• Damaged cable in the fan control circuit
• Loose or corroded plug connections
• Defective radiator fan motor
• Faulty engine control unit (ECU)
• Blown fuse in the fan circuit
• Defective coolant temperature sensor
• Short circuit in the wiring

What symptoms occur in parallel with fault code P0485?

• Engine overheating: The engine gets hotter than normal, especially when idling or driving slowly.
• Radiator fan not running: The electric radiator fan does not start when the engine warms up.
• Check engine light: The check engine light is permanently illuminated on the dashboard.
• Increased coolant temperature: The temperature display shows higher values than usual.
• Loss of power: The engine loses power, especially at higher temperatures.

How can the problem with error code P0485 be rectified?

• Repairing trouble code P0485 requires a systematic approach to identifying and eliminating the cause.
• Replace the cooling fan relay: Locate the defective relay in the fuse box and replace it with a new, compatible relay.
• Check and repair the wiring: Inspect all cables to the radiator fan for damage, short circuits or breaks and replace defective cables.
• Clean plug connections: Clean corroded or loose plugs on the fan motor and control unit and connect firmly.
• Replace the radiator fan motor: If the motor is defective, replace the complete fan motor including housing with a new part.
• Check fuses: Identify blown fuses in the fan circuit and replace with new fuses with the correct amperage.
• Replace coolant temperature sensor: Remove defective temperature sensor and replace with a new sensor, then bleed the system.