Fault code P0485 is called “Cooling Fan Power/Ground Circuit Malfunction” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0485
Error P0485 refers to a fault in the power supply circuit or the cooling fan ground. If this code is activated, there may be a problem with the radiator cooling fan.
When driving, enough air flows through the radiator to cool the engine efficiently. When the vehicle is stopped, such as at a stoplight, air is not flowing through the radiator and the engine begins to heat up.
The transmission control module (PCM) detects an increase in engine temperature, through the coolant temperature sensor (CTS). This sensor is located near the thermostat.
When the temperature reaches approximately 223°F, the PCM commands the cooling fan relay to turn on.
Code P0485 is set when an abnormal voltage is detected on the supply side or the ground side of the cooling fan circuit during normal fan operation. This may occur during low, medium, or high speed operation. This error applies only to electrical problems, including intermittent faults.
Symptoms of vehicle malfunctions
The main signal that an error P0485 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- Check engine control lamp on the control panel will light up (the code will be recorded in the memory as a fault).
- The engine has overheated.
- The air conditioning system is not working properly.
The severity of fault code P0485 is high, as there is a risk of overheating the vehicle engine, which may cause damage or complete failure of the engine.
Factors that can cause this error code
The error code P0485 can mean that one or more of the following problems have occurred:
- Wiring problem or connector damage.
- Corrosion of electrical wires or connections.
- Faulty cooling fan module.
- Problem with thermostat or water pump (pump).
- Faulty engine coolant temperature sensor.
- Sometimes the cause is faulty PCM module.
How to fix or reset OBD-2 code P0485
Some suggested steps for troubleshooting and fix the error code P0485:
- Connect an OBD-II scanner to the vehicle’s diagnostic connector and read all stored data and error codes.
- Clear the error codes from the computer memory and test-drive the vehicle to see if code P0485 appears again.
- If the error code appears again, visually inspect the electrical wires and connectors related to the cooling system.
- If necessary, repair or replace any shorted, broken, damaged, or corroded components.
- Test fan operation.
- Check engine coolant temperature sensor operation.
- Check the fan control relay and replace it if necessary.
- Test the battery and make sure the system voltage is normal.
- If the problem persists, check and replace the Power Control Module (PCM) if necessary.
Diagnose and repair of problems
The first step in the P0485 troubleshooting process is to review the Technical Service Bulletins (TSB). For known problems with a particular vehicle.
The advanced diagnostic steps are very vehicle specific. It may require, special equipment and knowledge to accurately perform the steps.
Many vehicles will have two fans, one used to cool the engine. And the second is for cooling the air conditioner condenser and additional engine cooling.
The fan that is not in front of the air conditioner condenser is the main cooling fan and should be focused on initially. Also, many cars have multi-speed fans. They can have up to three fan speed relays: low, medium and high.
Visual inspection
Open the hood and do a visual inspection. Look at the fan and make sure there are no obstructions blocking air flow in front of the radiator. Manually spin the fan, if it does not spin, there is most likely a problem with the bearings, they should be replaced.
Check the electrical connection of the fan. Disconnect the connector and inspect it for corrosion or bent contacts. Repair if necessary and apply dielectric grease to terminals.
Open the fuse box and inspect the cooling fan relay fuses. If they are OK, remove the cooling fan relay and test it. The bottom of the fuse box cover usually indicates the location.
Use an ohmmeter to check for continuity between the relay terminal on the fan side and the connector on the fan. If there is a signal, then the fan is defective. Otherwise, the harness between the fuse box and the fan is faulty.
Check the coolant temperature sensor (CTS) with an ohmmeter. Remove the connector, allow the engine to cool, and set the ohmmeter to the 200000 scale. Also check the sensor terminals.
If these steps failed to find the failure, there may be a bad connection to the PCM or the PCM itself is faulty. If this is the case, it is best to consult a technician for reprogramming or replacing the ECU.
On which vehicles does this problem occur most frequently
Fault code P0485 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Citroen (Berlingo, C3, C4, C5)
- Datsun (on-DO)
- Ford
- Mazda
- Mercedes-Benz
- Peugeot (206, 207, 307, 406, 407, Partner)
- Volvo (S60)
- LADA (Granta, Kalina, Priora, Vesta)
Fault code P0485 can sometimes be found with other errors. The most common are the following: P0480, P0481, P0482, P0483, P0484.
