**What Does It Mean?**
This is a generic diagnostic trouble code (DTC) for the powertrain, meaning it covers all makes/models from 1996 onward. However, specific troubleshooting steps vary by vehicle.
If your vehicle’s check engine light comes on and after retrieving the code you find a P0482 displayed, it refers to the engine cooling fan circuit. This is a generic code applying to all OBD-II (On-Board Diagnostic) vehicles.
While you are driving, sufficient air passes through the radiator and effectively cools the engine. When you stop the car, no air passes through the radiator and the engine begins to increase in temperature.
The PCM (Powertrain Control Module) detects the engine temperature increase via the CTS (Coolant Temperature Sensor) located near the thermostat. When the temperature reaches approximately 223 degrees F (the value depends on the make/model/engine), the PCM commands the cooling fan relay to activate the fan. It does this by providing ground to the relay.
There is a problem in this circuit causing the fan not to operate, allowing the engine to overheat while idling or driving at low speeds. When the PCM attempts to activate the fan and monitors the command and the result does not match, the code is set.
NOTE: P0482 refers to the main circuit, however codes P0480 and P0481 concern the same issue, the only difference being they relate to the different fan speed relays.
**Symptoms**
**Symptoms may include:**
* Check Engine Light illuminated (Malfunction Indicator Lamp) and P0482 code set
* Engine temperature increases when the vehicle is stopped and idling
**Potential Causes**
**Causes of this DTC may include:**
* Faulty Fan Control Relay 3
* Fan Control Relay harness is open or shorted
* Poor electrical connections in the circuit
* Faulty Cooling Fan 3
* Faulty Coolant Temperature Sensor
* Cooling Fan Fan harness is open or shorted
* Poor electrical connection in the Cooling Fan circuit
* Intake Air Temperature (IAT) sensor failure
* Air Conditioning Selector
* A/C Refrigerant Pressure Sensor
* Vehicle Speed Sensor (VSS)
**Diagnostic and Repair Procedures**
It is always wise to check the Technical Service Bulletins (TSBs) for your specific vehicle to see what types of complaints have been submitted to dealer service regarding this code. Search using your favorite search engine for “technical service bulletins for …..” Look for the code and the type of repair recommended by the manufacturer. This is also a good idea before purchasing a vehicle.
Many vehicles will have two engine fans, one for engine cooling and the second for air conditioning condenser cooling, 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 focus on initially. Additionally, many vehicles have multi-speed fans requiring up to three fan speed relays for low, medium, and high speeds.
Open the hood and perform a visual inspection. Look at the fan and ensure there is no obstruction in front of the radiator blocking airflow. Spin the fan with your finger (ensure the vehicle and key are off). If it does not spin, the fan bearings are seized and the fan is bad.
Check the electrical connection to the fan. Separate the connector and look for corrosion or bent pins. Repair if necessary and use dielectric grease on the terminals.
Open the fuse box and inspect the cooling fan relay fuses. If they are good, remove the cooling fan relays. The bottom of the fuse box cover will usually indicate the location, but if not, check the owner’s manual.
The function of the vehicle’s PCM is to act as a ground to operate components, not to provide power. The fan relays are nothing more than a remote lighting switch. The fan, along with other devices, draws too much amperage to be safely run into the cockpit, so it is kept under the hood.
A constant power supply from the battery is present on one terminal of each of the relays. This powers the fan when the circuit is closed. A switched power terminal will only be hot when the key is on. The ground terminal of this circuit is the one used when the PCM wants to activate the relay by grounding it.
Look at the circuit diagram printed on the side of the relay. Look for the simple open and closed circuit. Check for the positive battery terminal in the relay block with constant power. The opposite side goes to the fan. Use a test light to find the hot terminal.
Jump the battery terminal to the fan harness terminal and the fan should run. If not, disconnect the fan connection at the fan and using an ohmmeter, check for continuity between the fan side of the relay terminal and the fan connector. If there is continuity, the fan is bad. If not, the harness between the fuse block and the fan is faulty.
If the fan did run, check the relays. Look on the side of the relay for the switched power terminal or simply turn the key on. Check the terminals for another power terminal and see where it would be on the relay.
Jump the battery plus terminal from the first test with this switched terminal and place an additional jumper from the relay’s ground terminal to ground. The switch will click on. Use an ohmmeter to check that the constant battery terminal and the fan harness terminal have continuity, meaning the circuit is closed.
If the circuit did not close or the relay did not click, the relay is bad. Check all relays in the same manner to ensure they all function.
If there was no switched power to the relay, the ignition switch is suspect.
If they prove good, check the CTS with an ohmmeter. Remove the connector. Let the engine cool down and set the ohmmeter to the 200,000-ohm scale. Probe the sensor terminals.
The reading will be around 2.5. For accurate readings, consult a service manual. Accuracy is not necessary as all sensors can be different. You just want to know if it’s working. Plug it back in and warm up the engine.
Stop the engine and pull the CTS plug again. Check it with the ohmmeter, there should be a large change in resistance, if not the sensor is bad.
If the above procedure failed to find a fault, the likelihood is that a bad connection to the PCM or the PCM itself is at fault. Do not proceed further without consulting your service manual. Disconnecting the PCM can cause a loss of programming and the vehicle may not start unless towed to the dealer for reprogramming.