P0483 OBD-II Trouble Code: Cooling Fan Rationality Check Malfunction

P0483 code definition

The presence of the P0483 code in the PCM indicates that the PCM is detecting a voltage reading that is either too high or too low in the electrical cooling fan control circuit.

What the P0483 code means

The ECM, or Engine Control Module, regulates the electric cooling fan within the engine. This fan is responsible for cooling the engine once it reaches a specific temperature, for providing air conditioning, and will run when a variety of predetermined conditions occur. If the P0483 code is stored, it means that the cooling fan has been commanded to turn on or off, but the voltage reading indicates that the fan did not respond to the command.

What causes the P0483 code?

In most cases, the P0483 code is present when there is a bad cooling fan motor or faulty fan control relay.

Other causes may include:

• Faulty or loose connectors
• Faulty coolant temperature sensor
• Shorted electrical wiring
• Poor connection within the cooling fan circuit
• Open or shorted cooling fan harness
• Faulty power steering pump

What are the symptoms of the P0483 code?

If the PCM stores the P0483 code, it is likely that the vehicle would first display certain symptoms that include an illuminated Check Engine Light, on overheating engine, blown fuses, or a malfunctioning air conditioning system.

How does a mechanic diagnose the P0483 code?

The first step to diagnosing a detected P0483 code is to perform a visual inspection of the wiring and connectors between the ECM, the cooling fan, and the PCM. If any appear to be loose, corroded, or faulty, repairing or replacing them should be followed by clearing the code and retesting the system. If the P0483 code returns, then the technician should move on to other repair options. It’s important than any power steering leaks or pump failure be fixed before inspecting the coolant fan motor, because the motor is driven by the hydraulic pressure from the power steering pump.

Common mistakes when diagnosing the P0483 code

In many later model vehicles, the cooling fan relay has been recalled, or part of a technical service bulletin. However, it’s a common mistake for technicians to simply replace the cooling fan motors, as the mostly likely candidate for the P0483 code, rather than performing a total diagnosis and checking the relays.

How serious is the P0483 code?

The P0483 code indicates a very serious issue within the issue, and should be addressed immediately. If the cooling fan is not activating as it should to cool the engine, it could lead to engine malfunction or failure due to overheating. It can also make it dangerous and uncomfortable to drive in extremely warm weather if the air conditioning does not work properly.

What repairs can fix the P0483 code?

In order to repair the issues that cause the P0483 code, a technician may perform some or all of the following, being sure to clear the code and retest after each possible fix:

• Perform a voltage and ground test at the cooling fan motor.
• Test system fuses, and replace any that are blown.
• Check the relays and circuitry within the system, and repair or replace any as necessary.
• Check the engine temperature readings and compare with the manufacturer’s specifications. Repair or replace the coolant temperature sensor if these do not match.
• Inspect and test all wiring and switches that connect to the PCM. Repair or replace as necessary.
• Monitor the voltage of the fan by hand, and compare to the manufacturer’s specifications. If the numbers match, replace or repair the fan motor. If they do not match, replace or repair the rheostat or the resistor assembly.

Need help with a P0483 code?

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