P0483 Code: Cooling Fan Rationality Check Malfunction

Identifying what a trouble code means is important to properly fix the issues in your vehicle. If you recently encountered the P0483 code, this article will help you learn more about its meaning, possible causes, and common symptoms. 

What Does the P0483 Code Mean? 

The P0483 code is defined as “cooling fan rationality check malfunction.” It is usually triggered by your powertrain control module (PCM) when it detects that the current being drawn by the cooling fan control circuit is either too high or too low. This means that the cooling fan is operating differently from how the PCM intended.

P0483 on a 2006 Subaru

The meaning of code P0483 varies from manufacturer to manufacturer. On a 2006 Subaru, for example, a pure “rationality check” is used. If the engine coolant temperature is greater than or equal to 100°C (212°F) and the radiator fan command from the ECM changes from OFF to ON, the engine coolant temperature is monitored and expected to decrease. If it doesn’t, this code is set. That’s a simple rationality test.

P0483 on a 2006 Chevrolet Trailblazer

On a 2006 Chevy Trailblazer, P0483 is set when the difference between the commanded and actual cooling fan speeds are greater than 1000 rpm. In other words, the ECM/PCM is monitoring the speed of the fan (which is variable) and when the fan speed isn’t within range of the expected commanded window, this code is set.

The 2006 Ford cooling fan criteria for this code is very similar to the 2006 Chevy Trailblazer fan and the pinpoint test leads through a test of circuits, connectors, and components.

Our quick discussion about rationality checks and electric cooling fans can help you better understand how P0483 is set.

Note: Again, the definition of code P0483 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P0483 Code?

The definition indicates that there is a problem with the cooling fan, but it can also be caused by other components. Its list of common causes include: 

• Cooling fan control module failure 
• Cooling fan failure
• Cooling fan relay module failure
• Wiring issues
• Faulty thermostat or water pump
• Faulty PCM 

What are the Common Symptoms of the P0483 Code?

• Cooling fans are always turned on
• Engine overheating
• Check engine light is on

How to Diagnose the P0483 Code

While the definition of the code indicates that the cooling fan has a problem, identifying whether it’s caused by the cooling fan or the cooling fan module may be difficult for inexperienced users. To get an accurate diagnosis, you may want to consult a trusted mechanic. If you want to learn about diagnosing a P0483 code, you can check out the video below.

How to Fix the P0483 Code

Before you perform any repair, you’ll need to accurately diagnose the cause of the code. There isn’t usually an all-encompassing fix for any OBD-II code, which is why diagnosis is important. Otherwise, you might end up fixing or replacing a part that’s still functioning. 

Once you’ve identified the issue causing the P0483 code, you can then consult online auto repair resources and how-to guides for possible solutions. 

All vehicles are different. This means a fix for an OBD-II code for one vehicle may not be applicable for another. As a result, you should consult your vehicle’s repair manual when it comes to troubleshooting and repairing diagnostic trouble codes. Chilton repair manuals may also be useful. However, ALLDATA subscriptions are even better, as they provide detailed factory repair information for drivers who want to do repairs themselves.

Other Notes About P0483 

The definition of this code typically applies to all OBD-II equipped vehicles. They can show up more often in certain vehicle models made by Isuzu, Ford, Mazda, Mercedes Benz, and Subaru. 

There are other cooling fan-related trouble codes such as the P0480, P0481, P0482, P0484, and P0485.

A Quick Note About Rationality Checks

The ECM/PCM is always watching related inputs and comparing them to one another. For just one example of many, let’s say that on a vehicle that uses idle air control (IAC) and a MAF sensor. The ECM/PCM commands the IAC to increase idle airflow and idle speed, but the mass airflow input doesn’t reflect increased airflow. This indicates that either the MAF isn’t reliable or the IAC failed to increase airflow, and a code will be set based on the lack of MAF response.

About Electric Cooling Fans

Belt-driven engine cooling fans were the order of things until transversely mounted front wheel drive engines made electric cooling fans necessary. But belt driven fans rob power from the engine, and so electrically driven or electrically controlled fans have largely become the order of things even on linear mounted engines in gasoline powered vehicles.

Electrically driven cooling fans have a powerful DC motor driving a fan that draws air through the radiator and A/C condenser when the vehicle isn’t moving. Many vehicles will have two fans that work together. GM and Ford tended to use a trio of relays and two switches so that the fans could either run at half speed (in series) or full speed (parallel), depending on prevailing demands. These systems can also run just one fan rather than using both fans.

Some electric cooling fans use a special module to control the fan(s). But many vehicles still have viscous clutches that enable the fan to spin much slower than the driving pulley. Except that since the early 2000s, these viscous clutches are controlled by the ECM/PCM rather than with the old-fashioned integral bi-metal spring and valve affair used on older viscous fan systems. This kind of control enables the ECM/PCM to precisely control the speed of the cooling fan in a variable fashion rather than simply having one or two speeds.

Where to Get a New Cooling Fan Control Module to Clear Code P0483

If a bad cooling fan control module triggered the P0483 code, don’t put off replacing it to prevent fan and engine problems. For an OE-grade module that won’t break the bank, look no further than CarParts.com.

Our website makes it easy for car owners like you to find the right parts for your ride. Simply use our vehicle selector and search filters to view compatible modules with the brand and price you prefer. Our selection includes accurate and detailed fitment information, so you’re sure to get exactly what your car needs to get back on the road.

We make it a point to get all our auto parts from the most trusted manufacturers in the industry. In short, you won’t have to worry about your new cooling fan control module failing you any time soon.

On top of that, you won’t have to wait too long to get them either. All our parts are on hand and ready to ship from a distribution center near you to guarantee fast shipping.

Don’t hold off on addressing DTC P0483. Shop now to get your hands on a new cooling fan control module in no time!