Modern vehicles are packed with sensors to a point where every significant component has one. All of these sensors send data to the ECU (Engine Control Unit), which then uses that data to adjust performance. When something goes wrong with your car, these sensors will notify the ECU which will often trigger a check engine light code. The P0484 is one of those trouble codes, and it’s a serious one.
The P0484 code has to do with your cooling system. If ignored, it could lead to serious trouble and possibly a full engine rebuild. Here’s how you can diagnose this code on your own, and what you can do to fix it.
What is the P0484 Code, and What Does It Mean?
P0484 is the “cooling fan circuit over current code”. It means that there is too much electrical current flowing through the cooling fan circuit. Current is the rate at which electricity flows through a circuit.
Generally speaking, this code indicates that your cooling fan is working outside normal parameters. It could fail, or it could not engage when necessary, thus leaving your engine without the ability to cool itself when the vehicle is not moving. The golden rule of not having your car blow up on you is to check any check engine light code that you might get as soon as you see it. The p0484 is a code that can cost you an arm and a leg if you decide to ignore this unwritten rule.
Where is the Cooling Fan Located?
In most cars, the main cooling fan is mounted behind the radiator. Although the design differs drastically in some vehicles, this where you’ll find your radiator fan in most cars. That being said, cars that run high boost forced induction systems use an intercooler, while rear engine vehicles use rear fans and sometimes a front fan as well. All in all, consult your vehicle’s manual if you’re unsure.
All that said, modern vehicles have two cooling fans, one for the A/C condenser and one for the radiator. The condenser fan works together with the heat exchanger to heat or cool the cabin. Some older vehicles use a separate module to control the fan speed, but in most modern vehicles, this will be integrated into the ECU.
The benefit of having one integrated module is that it takes up less space and can be better protected against damage. The problem with this is that when it fails, replace the whole engine module, rather than just a fan module, which is often more expensive than what you paid for your vehicle if it’s used.
What Causes the P0484 Code?
An overflow of current in a circuit will usually blow a fuse or relay before damaging the PCM. This will break the circuit and prevent any electricity from flowing to and from the components. In saying this, the primary cause of a P0484 code is a blown fuse or a relay. However, what causes said fuses or relays to blow is the interesting bit. Here are some of the known culprits:
- Circuit damage
- Engine coolant temperature sensor failure
- Broken cooling fan
- Faulty Battery or PCM
- Faulty radiator motor
Circuit Damage
As with any electrical component, a break in the circuit causes the related trouble code to be logged by the computer. The P0484 can occur because of damage to the wiring harness, a blown fuse, or damage to the engine temperature sensor connector.
To prevent damage to the PCM or sensors, the fuse blows in the event of increased voltage or current. This is so common that we recommend that you replace the fuse even if the cause of the fault is something else.
Engine Coolant Temperature Sensor Failure
A faulty ECT (Engine Coolant Temperature) sensor has its own trouble code, however, it can cause a host of trouble codes, including a P0484. This is because a faulty sensor will often send voltage at fluctuating currents. An increase in engine temperature can also cause the PCM to store this fault.
Broken Cooling Fan or Fan Motor
The cooling fan is one of the major components of your cooling system. The fan’s main purpose is to turn on when the car is idle because there is no air flowing into the engine. If the fan doesn’t turn on or runs too slowly, the PCM will log a P0484 fault.
Of course, the condenser or radiator fan failing can cause this fault code because they are usually on the same circuit.
The radiator motor and cooling fan are closely related. If the cooling fan motor fails, the fan will stop working and cause a P0484 code.
What Are the Common Symptoms of P0484 Fault Code?
The symptoms of a P0484 code are common to any cooling-related components. This makes it difficult to diagnose as often the PCM will log multiple faults along with it. A few of the symptoms are:
- Check engine light
- Malfunctioning A/C
- Overheating engine
- Cooling fan on while driving
Check Engine Light
When the PCM stores a fault, the check engine light is illuminated. Some cars have specific lights that turn on when a component fails, like the ABS light, but when it comes to the P0484 code, it does not have a special light.
Malfunctioning A/C
If the condenser fan has failed, the A/C will experience issues or will not heat or cool sufficiently. A break in the circuit will also cause the A/C to malfunction as it uses the same wiring harness as the ECT sensor and radiator fan.
Overheating Engine
The radiator fan is the only component that cools your engine when it is idling. If there is no cooling on idle the engine will overheat and log the P0484 code. However, keep in mind that engine overheating can be caused by other issues such as a cracked radiator, failed thermostat, or low coolant levels. Depending on what you drive, some of these may not even trigger a CEL despite being critical faults.
Cooling Fan On While Driving
This symptom is the clearest indicator of a fan circuit failure. The ECT (Engine Coolant Temperature) sensor failing causes the wrong coolant temperature to be communicated to the PCM. It will run the fan even when the coolant is below operating temperature.
How to Diagnose and Fix the Cause of P0484 Code?
Diagnosing the root cause of a P0484 code is fairly difficult. Mainly because it usually presents alongside a few other cooling-related codes. There are some simple methods that you can use to bring you closer to clearing the P0484 and bringing your car back to full health.
Wiring Damage
Living in a remote area has its perks, but one negative is that you encounter a lot of unwanted wildlife. Rodents often chew on wires to sharpen their teeth. The wiring harness in your engine bay is susceptible as the warmth of the engine attracts them, and it’s easily accessible. It’s extremely common and often ignored.
Look for any damage to your wiring harness or sensor connectors. Any exposed wiring and disconnected or damaged connectors will cause your P0484 code.
Fan Motor and Fan Damage.
Of course, if your radiator or A/C fan is cracked, then you should replace it. However, even though an odd rock can make quick work of your radiator, this is an unlikely scenario. It is far more likely that your fan motor has failed, and the fan is not spinning.
A unique way of diagnosing this is by looking at the live data of your vehicle on idle using an ODB II reader. If the fan does not turn on once the engine reaches operating temperature and there is no external damage, it means that your fan motor could be faulty given that everything else is working as it should (ECT more than anything else)
You can also control your fan speed using an ODB II reader and turn it on manually. It will not run if your fan motor has failed. It’s also important to note that the fan motor failure is the one unique cause of the P0484 code, so you should replace it first along with the related relay when repairing your vehicle.
In some cases, the A/C fan can also be manually controlled using the ODB II reader if you find your radiator fan works correctly.
Sensor Damage
The ECT sensor is the main sensor on the fan circuit. A failing one will give you the P0484 code. If the sensor is damaged or the plastic melted, replace it.
Testing it with a multimeter is more conclusive than an inspection test. Luckily for you, we have a full guide on diagnosing an engine coolant temperature sensor. In short, you should get around 5V when back probing your sensor connector and around 300 ohms from your sensor at operating temperature.
Fuse and Relay Test
The root cause of a P0484 is usually not a failed fuse or relay, as they fail, to protect the PCM from damage in the event of surges. These are the cheapest and easiest components to diagnose, and you must check them after swapping out the other electrical components.
Replacing fuses and relays first will probably extend the time it takes to repair your vehicle as they will keep failing as long as the root cause exists. A bad battery is one of the main causes of electrical issues, so that should also be checked before testing your relay.
Damage to the relay contacts or a melted fuse are signs that they have failed. Now, it’s important to remember that not all relays are made equal. The relays in your vehicle are specifically designed for them and swapping them out willy-nilly can cause damage to other components, including your PCM.
Buying the same relay that was originally in your vehicle will prevent further damage. Fuses are different. As long as you replace them with the same voltage and amperage, you can source them from anywhere.
Does P0484 Clear Itself?
Once the root cause has been repaired, the engine computer will compare predicted and actual fan readings on idle and clear the code itself. Alternatively, you can clear the code manually using an ODB II reader.
Can You Drive with P0484 Code?
Driving with an overheating engine is not something you want to even entertain. It is possible to drive a short distance as the airflow from the motion of the car will cool the engine, however as soon as you stop, your engine will overheat. This can lead to you having to replace the engine or expensive components, such as the PCM.
The cooling fan, fuses, and relays are cheap to replace and even the fan motor and ECT sensor are cheap compared to a complete engine replacement. So we would not advise you to drive with a P0484 code.
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