Error Code P0494 is defined as Fan Speed Low, which basically means the vehicle’s computer has detected a problem with low voltage reading coming from the electric cooling fan control circuit.


This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system or vehicles made since 1996 up to the present. It is usually found among Acura, BMW, Buick, Citroen, Chevrolet, Dodge, Ford, Peugeot, Toyota, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

Generally, the fan is mounted on the radiator, and it works by regulating the temperature of the engine by cooling the coolant in the radiator.

The PCM (powertrain control module, also known as ECM or engine control module in other makes) monitors and controls multiple sensors to keep the right temperature of the engine. One of which is the fan, which it switches on as the engine gets high (i.e. during idle at traffic), and off when there is sufficient airflow to keep the temperature down (cruising down the highway).

When the PCM detects a low fan speed (10% slower than the parameters set by the manufacturer) for the current driving condition, then it will store the Error Code P0494 and activate the Check Engine light simultaneously.

Other related Error Codes include:

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other common symptoms would include:

  • Engine overheat condition
  • AC not working efficiently
  • Engine noises
  • Poor engine performance
  • Engine misfiring
  • Stalling
  • Increase in fuel consumption

Possible Causes

Many times this code is simply caused by a bad cooling fan motor or defective cooling fan relay. There are, however, some less common causes, such as:

  • Corroded, damaged, or loose electrical connectors
  • Defective engine coolant temperature sensor
  • Open or shorted electrical wiring (which may or may not come with a blown fuse)
  • Defective cooling fan control unit
  • Defective cooling fan clutch

How to Check

As with most error codes, proper diagnosis for this code starts with confirming the existence of the code in the vehicle’s memory using an OBD-II scanner.

Then, mechanics proceed on conducting a thorough visual inspection of the wirings and all related electrical components in the electronic fan system, including all the vacuum lines and hoses. Any electrical issues, no matter how simple they may be, such as loose or shorted elements, must be repaired, if not replaced.

After doing any repairs, the codes must be cleared, and the vehicle must be tested again to see if the code comes back.

If the code comes back, then mechanics will proceed on checking the primary cooling fan motor. Then, he will check the voltage readings of the engine cooling fan relay. If either of the parts do not meet the requirements set by the manufacturer, then they must be replaced.

Next, the mechanic will proceed on diagnosing and retesting the system after each possible diagnosis.

Also, the PCM must be checked as well for signs of damage or corrosion.

How to Fix

Common repairs for this code include:

  • Repair or replacement of open or shorted electrical wiring
  • Replacement of faulty cooling fan motor
  • Replacement of faulty cooling fan relay
  • Repair or loose or corroded electrical connectors
  • Replacement of defective engine coolant temperature sensor
  • Replacement of defective cooling fan clutch
  • Replacement of defective cooling fan control unit

This error code is a serious problem, which means it must be addressed as soon as possible. Though there may be no obvious and dangerous symptoms at first, the inability to measure and control the temperature of the cooling system can lead to serious, larger, and more expensive problems.