P0481 Cooling Fan Relay 2 Control Circuit
OBD-II Trouble Code Technical Description
Cooling Fan Relay 2 Control Circuit
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC), which means it covers all makes/models, 1996-newer. However, specific troubleshooting steps will vary depending on the vehicle.
If your vehicle's check engine light comes on and after pulling the code you find a P0481 displayed, if refers to the engine cooling fan circuit. It is a generic code applying to all OBD II (on board diagnostics) vehicles.
While you are driving, air in sufficient quantity is passing through the radiator effectively cooling the engine. When you bring the car to a stop no air is passing through the radiator and the engine begins to increase in temperature.
The PCM (powertrain control module) senses the increase in engine temperature through the CTS (coolant temperature sensor) located near the thermostat. When the temperature reaches about 223-degrees F (value depends on make/model/engine), the PCM will command the cooling fan relay to turn on the fan. It does so by supplying the ground to the relay.
There is a problem within this circuit causing the fan to fail to operate allowing the engine to overheat while sitting still or driving at a slow speed. When the PCM attempts to activate the fan and senses the command and the result do not match, the code is set.
NOTE: P0481 speaks of the basic circuit, however codes P0480 and P0482 relate to the same problem with the only difference is they relate to the different fan speed relays.
Symptoms
Symptoms may include:
Check engine light (malfunction indicator lamp) illumination and code P0481 set Engine temperature will rise when the vehicle stops and idlesPotential Causes
The causes for this DTC may include:
Faulty fan control relay 2 Fan control relay harness is open or shorted Circuit electrical connections poor Faulty cooling fan 2 Faulty coolant temperature sensor Fan cooling fan harness is open or shorted Cooling fan circuit poor electrical connection Intake air temperature (IAT) failure A/C selector switch A/C refrigerant pressure sensor Vehicle speed sensor (VSS)Diagnostic and Repair Procedures
It is always a wise idea to look up the technical service bulletins (TSB) on your particular vehicle to see what type complaints have been coming in to the dealer service department related to this code. Search using your favorite search engine "technical service bulletins for .." Look up the code and the type of manufacturer recommended repair. This is also a good idea before buying a vehicle.
Many vehicles will have two engine fans, one for engine cooling and the second for cooling the air conditioning condenser, and additional cooling for the engine.
The fan that is not in front of the air conditioning condenser is the main cooling fan and the one to concentrate on initially. Additionally, many vehicles have multi-speed fans requiring as many as three fan speed relays for low, medium and high.
Open the hood and do a visual inspection. Look at the fan and make sure there is no obstruction in front of the radiator blocking airflow. Spin the fan with your finger (make sure the vehicle and key is off). If it will not spin the fan bearings are shot and the fan is bad.
Check the electrical connection at the fan. Pull the connector apart and look for corrosion or bent pins. Repair if necessary and use dielectric grease on the terminals.
Open the fuse block and inspect the cooling fan relay fuses. If they are good pull the cooling fan relays out. The bottom of the fuse block lid will usually indicate placement, but if not, look in the owner's manual.
The vehicle's PCM's function is to act as a ground to operate components, not to supply power. The fan relays are nothing
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