Fault code P0494 – fan speed low

Fault code P0494 is called “Fan Speed Low” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0494

OBD-II fault code P0494 is a generic fault code that is defined as “low cooling fan speed”. It is set when the Powertrain Control Module (PCM) detects that the radiator cooling fan is not rotating at the required speed.

Fault code P0494 – fan speed low

The cooling fan is designed to reduce the temperature of the engine coolant as it passes through the radiator. Depending on the temperature of the engine coolant, the fan can operate at different speeds.

The fan motor can turn on in several ways, depending on operating conditions. But regardless of the design features, the PCM controls the fan speed while the fan is running.

The control module turns the fan on when the motor temperature rises, such as when idling. And it turns it off when the airflow is sufficient to reduce the temperature, such as when driving on the highway.

Code P0494 is set when the PCM detects that the actual fan speed deviates from the desired speed by about 10%. And refers to electrically driven radiator fans, not viscous or belt driven fans.

Symptoms of vehicle malfunctions

The main signal that an error P0494 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
  2. The air conditioning system may not work properly.
  3. The vehicle’s engine may overheat.
  4. Additional engine noises.
  5. Engine stalls or starts poorly.
  6. Jerking/missing ignition.
  7. Increased fuel consumption.
  8. Decrease of the engine power capacity.

Error P0494 is quite serious because it affects the cooling system, which is not working properly. Therefore, there is a risk of engine overheating, which can lead to damage of important components as well as costly repairs.

Factors that can cause this error code

The error code P0494 can mean that one or more of the following problems have occurred:

  • The fan motor is defective.
  • Cooling fan relay is defective.
  • Damaged, burned, shorted, or corroded wiring.
  • Problem with connector.
  • Faulty engine coolant temperature sensor.
  • Sometimes a faulty PCM module is the cause.

How to fix or reset OBD-2 code P0494

Some suggested steps for troubleshooting and fix the error code P0494:

  1. Connect an OBD-II scanner to the vehicle’s diagnostic connector and read all stored data and error codes.
  2. Visually inspect the electrical wiring and connectors related to the cooling system.
  3. If necessary, repair or replace any shorted, broken, damaged or corroded components.
  4. Check the fan motor and relay.
  5. Test the engine coolant temperature sensor.

Diagnose and repair of problems

In order to detect error P0494 it is necessary to record all available fault codes as well as all available freeze frame data. This information may come in handy if a recurring fault is subsequently detected.

Faulty fan switches often cause this fault, a jumper should be installed between the ground and the power wire to check the circuit. If the fan motor and circuits are OK, the fan will start and run at the correct speed when the jumper is inserted.

If the fan motor does not start when the jumper is shorted, several faulty components can be assumed. A faulty fan switch, fan motor relay, fuse, broken wiring, resistor, or fan motor itself.

Check electrical components

Check all fuses, but do not replace blown fuses until a short circuit or electrical overload is found and corrected. Locate the relay and check its resistance according to the instructions in the manual.

Replace the relay to ensure proper operation of the system if any electrical values do not match those in the manual. Test the system after replacing the relay to ensure that the radiator fan operates as intended.

If the fan relay is checked and there are no blown fuses, check the internal resistance and integrity of the fan motor. Lack of continuity means the motor has an internal open circuit, and abnormal resistance may indicate an internal short circuit.

After checking the fan motor, perform a resistance, continuity, and ground check on all associated wiring. Also check for damaged, burned, shorted, disconnected, or corroded connectors.

By following these steps, it is likely that code P0494 will be corrected, but in rare cases, if the fault persists, there may be intermittent faults. Such malfunctions can be very difficult to troubleshoot, so it is better to contact the service for professional diagnosis and repair.

On which vehicles does this problem occur most frequently

Fault code P0494 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Acura
  • BMW
  • Buick
  • Chevrolet
  • Citroen (Berlingo, C3, C4, Cactus, Picasso)
  • Dodge
  • Ford
  • Honda
  • Peugeot (207, 3008, 301, 308, 408, 5008, 508, Expert, Partner)
  • Toyota

Fault code P0494 can sometimes be found with other errors. The most common are the following: P0493, P0495.


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