P0483 Cooling Fan Rationality Check Malfunction Trouble Code

P0483 Cooling Fan Rationality Check Malfunction

OBD-II Trouble Code Technical Description

Cooling Fan Rationality Check Malfunction

What does that mean?

This generic powertrain/engine diagnostic trouble code typically applies to all OBDII equipped engines, but shows up more often in certain Ford, Isuzu, Mazda, Mercedes Benz, and Subaru vehicles.

The Cooling Fan Module is usually found mounted behind the radiator in front of the engine. The Cooling Fan Module is typically controlled by the Powertrain Control Module (PCM) based upon inputs wired to it.

 

The PCM receives these inputs via voltage signals to determine engine coolant and intake air temperature, air conditioner pressures, and vehicle speed. This code is set if these inputs do not match normal operating voltages stored in the PCM’s memory, or if the cooling fan operation does not match the predetermined information stored in the PCM.

P0483 could have been set because of mechanical temperature issues (incorrect coolant temperature due to stuck thermostat/failed water pump); or electrical issues (failed cooling fan circuit). These cannot be overlooked in the troubleshooting stage, especially when dealing with an intermittent problem. Troubleshooting steps may vary depending upon manufacturer, type of cooling fan module and wire colors.

Related cooling fan trouble codes include:

P0480 Cooling Fan 1 Control Circuit Malfunction P0481 Cooling Fan 2 Control Circuit Malfunction P0482 Cooling Fan 3 Control Circuit Malfunction P0484 Cooling Fan Circuit Over Current P0485 Cooling Fan Power/Ground Circuit Malfunction

Severity & Symptoms

Severity depends upon the failure. If a mechanical failure; severe. If an electrical failure, it may not be as severe, as the PCM can compensate for it, as long as the engine does not overheat. While the PCM is compensating, the temperature gauge must be monitored during all drive cycles. Typically, the fans operate all the time (100 % duty cycle).

Symptoms of a P0483 trouble code may include:

Malfunction Indicator Light On Engine Overheating A/C system not functioning properly

Potential Causes

Typically the causes for this code to set are:

Open in the power supply circuit between the cooling fan module and the PCM – possible Short to ground in the power supply circuit to the cooling fan module - possible Cooling system malfunction – faulty thermostat/water pump – most likely Cooling fan module faulty - possible Faulty PCM - highly unlikely

Diagnostic and Repair Procedures

A good starting point is always a technical service bulletin (TSB) search for your particular vehicle. The vehicle manufacturer may have a PCM flash/reprogram to cover this issue, and it pays to check on this before you find you’ve gone down a long/wrong path.

Next, locate the cooling fan module on 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 scraping, rubbing, bare wires, burn spots or melted plastic. Pull the connectors apart and carefully inspect the terminals (the metal parts) inside the connectors. See if they look burned or have a green tint indicating corrosion. Use electrical contact cleaner and a plastic bristle brush if cleaning of the terminals is needed. Let dry and apply electrical grease where the terminals contact.

If you have a scan tool, clear the diagnostic trouble codes from memory, and see if P0483 returns. If it does not, then the connections were most likely your problem.

If the code does return, verify the integrity of the cooling system. Insure that the thermostat and the water pump are functioning properly. Once the engine has cooled, remove the radiator cap and insure that it will seal properly to the radiator. If there are an

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