Error Code P0485: What It Means & What To Do?

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P0485 is a diagnostic trouble code (DTC) for "Cooling Fan Power/Ground Circuit Malfunction". This code is set when abnormal voltages are detected during normal fan operation on the power side/ground side of the cooling fan circuit. This error code generally happens when the BSI detects the fan is not functioning as it should. This code is only concerned with electrical issues (failed cooling fan circuit), including intermittent problems.

OBD-II Code Cooling fans may stay on all the time is defined as a Fan Power/Ground Circuit. This code is detected when the PCM detects that the commanded state of the driver and the actual state of the control circuit do not match. It indicates abnormal voltages are detected during normal fan operation on the power side/ground side of the cooling fan circuit. It usually happens during low, medium or high-speed operation. Main symptom of this code is Overheating of engine which should be addressed on time else can lead to serious and expensive repairs. Check engine light illuminate as well once the code is stored however if there is a code stored and no service engine soon lamp, the code may be displayed as a pending code.

What causes this problem of Cooling Fan Power/Ground Circuit Malfunction?

• Cooling fan failure
• Defective fan control relay or fan control circuit
• Open or shorted fan control relay harness
• Poor electrical connections

1. Fan Control Relay - The relay is the component that fails most often, so be sure to test the relay as well as its power supply and ground connections and replace the faulty one immediately.
2. Cooling Fan - A radiator cooling fan is device that can help regulate engine temperature by pulling air through a radiator. Make sure its efficient functionality to avoid all the related codes.
3. Cooling Fan Harness - A defective cooling fan harness could also be causes of storing trouble code so make sure it should work efficiently.
4. Cooling Fan Connector - It might be a small component but could be the main cause for storing this code. Always replace the damaged connectors to avoid any trouble code.

Some common symptoms which help you identify the trouble code P0485 are listed below:

• Reduced efficiency of AC
• Overheated engine
• Blown fuses
• Illuminated check engine light

Trouble code P0485 requires your immediate attention and needs to be resolved as soon as you discover it to avoid expensive repairs. It may require diagnostic tools to inspect it and probably some important replacements as well so it is always recommended to have it fixed by an experienced technician. Some important repairs and replacements to fix this code are as follows:

• Locate the cooling fan first and replace it if found faulty.
• Remove all the wires and housing that connects the engine to the fan, if it is damaged repair or replace it as required.
• Inspect the fan motor, if it is inoperative; repair or replace it immediately.
• Inspect all the fuses and relays and replace the faulty ones.
• Once done with all the required repairs and replacements, clear the code and retest it. If required take the help of experienced technician.

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Steps to diagnose this error code are as follows:

• Begin with visual inspection and look at the fan to make sure there is no obstruction in front of the radiator blocking airflow.
• Inspect the electrical connection at the fan. Pull the connector apart and look for corrosion or bent pins. Repair if necessary.
• Open the fuse block and inspect the cooling fan relay fuses.
• Look at the circuit diagram displayed for the simple open and shut circuit.
• Verify the battery positive terminal in the relay block with constant power and use a test light to find the hot terminal.
• Jump the battery terminal to the fan harness terminal and the fan will operate.
• If not, disconnect the fan connection at the fan and using an ohmmeter check the continuity between the fan side of the relay terminal and the connector at the fan.
• Check all the relays in the same fashion to be sure they are all working.
• Jump the battery plus terminal in the first test with this switched terminal and place an additional jumper from the negative terminal on the relay to ground.
• If the circuit has not closed or the relay has not clicked, the relay is bad.
• If there was no switched power at the relay, the ignition switch is suspect.
• Check the CTS with an ohmmeter and probe the sensor terminals.
• Shut the engine down and pull the CTS plug again. Check it with the ohmmeter, there should be a big change in resistance, if not the sensor is bad.
• If the above procedure could not find a failure, the probability is that a poor connection to the PCM or the PCM itself is at fault.

Common Mistakes When Diagnosing the P0485 Code

The most common mistake is not diagnosing the vehicle as per steps. Missing the steps actually leads to unnecessary replacements. So, it is crucial to have your vehicle diagnosed from an experienced diagnostician.