Technical Description of OBD-II Trouble Code
Excessive Current in Cooling Fan Circuit
What does that signify?
This generic powertrain/engine diagnostic trouble code is applicable to all OBDII equipped engines, but it is more commonly observed in certain Mazda and Mercedes Benz vehicles.
The Cooling Fan Module is typically located behind the radiator in front of the engine. The Powertrain Control Module (PCM) usually controls the Cooling Fan Module based on the inputs it receives.
The PCM receives voltage signals to determine engine coolant and intake air temperature, air conditioner pressures, and vehicle speed. This code is triggered if these inputs do not match the normal operating voltages stored in the PCM’s memory, or if the cooling fan operation does not align with the predetermined information stored in the PCM.
P0484 is set when an excessive amount of current is detected during normal fan operation. This can occur during low, medium, or high-speed operation. This also includes vehicles that use fan relays to operate the cooling fans. This code specifically relates to electrical issues (failed cooling fan circuit), including intermittent problems. Troubleshooting steps may vary depending on the manufacturer, type of cooling fan module, and wire colors.
Related cooling fan trouble codes include:
Severity & Symptoms
The severity depends on the nature of the failure. In the case of an electrical failure, it may not be considered severe as the PCM can compensate for it, unless the engine starts to overheat. While the PCM is compensating, the temperature gauge must be monitored during all drive cycles. Typically, the fans operate continuously (100% duty cycle).
Symptoms of a P0484 trouble code may include:
Potential Causes
The typical causes for this code to be triggered are:
Diagnostic and Repair Procedures
A good starting point is always to search for any technical service bulletins (TSBs) related to your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogram to address this issue, and it is advisable to check this before pursuing other troubleshooting steps.
Next, locate the cooling fan module in your particular vehicle. The Cooling Fan Module (cooling fans) is usually found mounted behind the radiator in front of the engine. Once located, visually inspect the connectors and wiring. Look for any signs of scraping, rubbing, bare wires, burn spots, or melted plastic. Disconnect the connectors and carefully examine the terminals inside. Check for any signs of burning or corrosion. If needed, clean the terminals using electrical contact cleaner and a plastic bristle brush. Allow them to dry and apply electrical grease to the contact points.
If you have a scan tool, clear the diagnostic trouble codes from memory and check if P0484 reappears. If it does not, then the issue was most likely related to the connections.
If the code does reappear, further testing of the fans and their associated circuits is necessary. Typically, there are 2 wires connected to each cooling fan in the module. First, disconnect the harness going to the cooling fan module. Using a Digital Volt Ohm Meter (DVOM), connect one lead of the meter to one terminal of one of the fans and connect the remaining meter lead to the other fan terminal. There should be no open circuit or short circuit. Verify the resistance specifications for your specific vehicle. If the fan motor is either open or shorted (infinite resistance or 0 ohms), replace the cooling fan module or, if available, the cooling fan motor.
If that test passes, use a DVOM to check if there is 12V in the cooling fan module power supply circuit (Red lead to the fan power supply circuit, black lead to a good ground). Use a scan tool that can activate the cooling fans to turn them on. If there is no 12 volts reaching the fan, repair the wiring from the PCM or relay to the fan, or consider the possibility of a faulty PCM.
If that is okay, check if there is a good ground at the cooling fan module. Connect a test light to the positive terminal of a 12V battery and touch the other end of the test light to the ground circuit going to the cooling fan module. Use the scan tool to activate the cooling fan module and observe if the test light illuminates each time the fan is activated. If the test light does not illuminate, it indicates a problem with the circuit. If it does illuminate, wiggle the wiring harness going to the fan to check if the test light flickers, indicating an intermittent connection.
If all the tests have been passed so far and the P0484 code continues to appear, it is likely that the cooling fan module has failed. However, the possibility of a faulty PCM cannot be ruled out until the fan has been replaced. If unsure, it is recommended to seek assistance from a trained automotive diagnostician. PCMs must be programmed or calibrated to the vehicle in order to be installed correctly.
