Cooling Fan Circuit Over Current
The cooling fan is drawing too much electrical current, like a circuit breaker tripping when you plug in too many devices. The ECU detected the fan motor or its control circuit is consuming more power than it should.
The ECU monitors current draw through the cooling fan relay circuit using an inline current sense circuit or by measuring voltage drop across a shunt resistor. When current exceeds the programmed threshold (typically 15-20 amps depending on fan type), the ECU sets this fault code. The measurement occurs during fan operation to detect shorts, seized fan motors, or relay failures.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Cooling Fan Current Draw | 8-15 amps (depends on fan type) | Above 15-20 amps or continuous high current |
| Fan Relay Voltage Drop | Less than 0.5V across contacts | Above 1.0V indicating high resistance/arcing |
Code P0485 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0485 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.