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Error Code P0481 is defined as Cooling Fan 2 Control Circuit Malfunction. This trouble code refers to the engine cooling fan circuit, as it experiences a malfunction causing the fan to fail, which then leads to engine to overheat.
This code is a generic trouble code, which means it applies to all vehicles equipped with OBD-II scanner, or vehicles made since 1996 up to present. Specifications on the definition, troubleshooting and repairs of course, vary from one make/model to another.
As the vehicle runs, the radiator and the engine are both being cooled by the air with sufficient quality as it passes through. When the vehicle idles or stops, there will be no air to pass through the radiator. This is where the purpose of the fans kicks in – to provide ample cooling for both the radiator and engine to keep them from overheating.
The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) senses this increase in temperature through the CTS (coolant temperature sensor) located near the thermostat. If the temperature reaches more than 223˚ F (value depends on make, model or engine of the vehicle), the PCM automatically command the cooling fan relay to turn on its fan by supplying the ground to the relay.
Should there any problem within the circuit that will cause the fan to fail, the engine will heat up, causing it to overheat. This can happen whether the vehicle is sitting still or driving at slow speed.
Basically, the Error Code P0481means the cooling fan 2 control circuit has experienced a problem, causing it to malfunction. The vehicle’s PCM control the cooling fans, and the second that it determines the fans are not working properly, it triggers the code and illuminates the Check Engine light.
As with other error codes, this code triggers the Check Engine light. Aside from that, the only obvious symptom for this code is the increase of engine temperature each time the vehicle comes to stop or idles, this is because the fans are not running to cool off the engine.
There are multiple factors that can lead to this error code, some of the most common possible causes are:
- Open or shorted fan control relay harness
- Open or shorted fan cooling fan harness
- Defective faulty fan control relay 2
- Faulty cooling fan 2
- Poor electrical connections in the cooling fan circuit
- Defective coolant temperature sensor
- IAT (intake air temperature) failure
- A/C selector switch
- A/C refrigerant pressure sensor
- Faulty VSS (vehicle speed sensor)
How to Check
To diagnose this error code, mechanics use a scan tool to check for any codes present in the PCM. They also take note of the freeze frame data that shows the vehicle’s conditions when the code was set, such as RPM, vehicle speed, coolant temperature, etc.
Next, they clear the codes and then take the vehicle for a test drive to duplicate the conditions when the code was set.
Then, they conduct a visual inspection of the fan system; this includes checking the fan’s operation and looks for any signs of damage and wear and tear.
Then, they use the scan tool to check the datastream and confirm the VSS sensor has proper readings, and if the coolant temperature sensor is reading accurately.
Then they test the fan control relay using a relay tested, or switch the relay using a good relay to test.
Next, they check the AC pressure switch for proper operation, and if it’s reading within the specs.
How to Fix
Repairs for this error code are pretty simple and straightforward, which of course, can be derived from a thorough diagnosis. Some of the usual repairs are:
- Repair or replacement of fan wiring harness
- Replacement of cooling fan 2
- Replacement of the VSS sensor
- Replacement of engine coolant temperature sensor
- Replacement of AC pressure sensor switch
- Repair of electrical connection problems
- Replacement of fan control relay
The most common mistake people commit when dealing with this error code is skipping steps from the diagnosis. There are many systems involved in this error code, which is why it is crucial to pinpoint which component is causing the problem.