Technical Description of OBD-II Trouble Code
Malfunction in the Cooling Fan Rationality Check
What does that signify?
This generic powertrain/engine diagnostic trouble code is typically applicable to all OBDII equipped engines, but it is more commonly observed in certain Ford, Isuzu, Mazda, Mercedes Benz, and Subaru 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 wired to it.
The PCM receives voltage signals from these inputs to determine the 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.
P0483 may be set due to mechanical temperature issues (such as incorrect coolant temperature caused by a stuck thermostat or failed water pump) or electrical issues (such as a failed cooling fan circuit). These factors should not be overlooked during the troubleshooting stage, especially when dealing with an intermittent problem. The 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 type of failure. If it is a mechanical failure, it can be severe. If it is an electrical failure, it may not be as severe because the PCM can compensate for it as long as the engine does not overheat. However, the temperature gauge must be monitored during all drive cycles while the PCM is compensating. Typically, the fans operate continuously with a 100% duty cycle.
Symptoms of a P0483 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 a technical service bulletin (TSB) related to your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogram to address this issue, so it is worth checking before going down a potentially incorrect path.
Next, locate the cooling fan module in your specific 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 scraping, rubbing, bare wires, burn spots, or melted plastic. Disconnect the connectors and carefully inspect the terminals inside. Check for any signs of burning or corrosion (indicated by a green tint). If cleaning of the terminals is necessary, use 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 see if P0483 returns. If it does not, then the problem was most likely related to the connections.
If the code does return, verify the integrity of the cooling system. Ensure that the thermostat and water pump are functioning properly. Once the engine has cooled, remove the radiator cap and ensure that it seals properly to the radiator. If there are any doubts about these cooling system components, replace them first as they are the most common areas of concern related to this fault code. After replacing them, clear the codes and test drive the vehicle to ensure that P0483 does not reappear.
If the code does reappear, the fans and their associated circuits need to be tested. Typically, there are 2 wires at 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 or shorted 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 to 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 12V battery positive (red terminal) and touch the other end of the test light to the ground circuit going to the cooling fan module circuit ground. Use the scan tool to actuate the cooling fan module and see if the test light comes on each time the scan tool activates the fan. If the test light does not light up, it indicates a problem with the circuit. If it does light up, wiggle the wiring harness going to the fan to see if the test light flickers, indicating an intermittent connection.
If all the tests have passed so far and you continue to receive a P0483 code, it most likely indicates a failed cooling fan module. However, a failed PCM cannot be ruled out until the fan has been replaced. If unsure, seek assistance from a trained automotive diagnostician. PCMs must be programmed or calibrated to the vehicle in order to be installed correctly.
