OBD-II Trouble Code Technical Description
The fan speed is operating at a low level.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles such as Chevrolet, Buick, Peugeot, Toyota, Citroen, Dodge, BMW, Honda, Acura, Ford, and Dodge. While the code is generic, the specific repair steps may vary depending on the make and model of the vehicle.
The cooling fan, which is mounted on the radiator, is the fan referred to in these codes. Its purpose is to cool down the coolant in the radiator and help regulate the engine temperature.
The engine control module (ECM) or powertrain control module (PCM) monitors and controls various sensors to regulate the engine temperature. The ECM activates the fan when the engine temperature rises, such as when idling in traffic, and deactivates it when there is sufficient airflow to keep the temperature down, such as when cruising on the highway.
The ECM has detected a low speed condition in the cooling fan. If the fan is spinning outside of the manufacturer’s set parameters, the ECM will illuminate the engine light or malfunction indicator lamp (MIL).
Related engine cooling fan diagnostic codes:
Symptoms
Symptoms of a P0494 engine code may include:
Potential Causes
The typical causes for this code to be set are:
Diagnostic and Repair Procedures
When working with electrical systems, it is recommended to have the following basic tools:
Safety Tips
Basic Step #1
Perform a visual inspection. Open the hood and locate the radiator/fan assembly, which is usually mounted at the front of the vehicle, directly in front of the engine. Note that there are different styles and setups for cooling fans, some mounted directly on the radiator and others belt-driven by the engine. Inspect the fan(s) and blades for any damage. Shake one of the fan blades lightly to check for play in the bearings. Depending on the style and amount of play, the fan assembly may need to be replaced. Also, inspect the shroud and anything that may obstruct the fan’s performance. Pay close attention to the wiring harness for the cooling fan, as even one lightly frayed wire can trigger codes. If everything appears to be in good condition, proceed to the next step.
TIP: Aftermarket shrouds may not fit perfectly, causing the fan to rub against parts of the shroud and resulting in a low speed condition. With the engine off and cold, spin the fan by hand. It should spin freely in the shroud (you may need to remove the belt for the belt-driven version).
Basic Step #2
Check the connector. Before performing any repairs or tests on the electrical system, ensure that the battery is disconnected. Follow the harness coming out of the cooling fan until you find its connector. Inspect the connector for signs of overheating, melting, or corrosion. Disconnect the connector and inspect the pins inside. Repair or replace any corroded or bent pins. If the connector is damaged, it will likely need to be replaced. If everything looks fine, proceed to the next step.
TIP: Ensure that your electrical system is in good condition. Keep in mind that a weak battery or a problem with the charging system can cause the ECM to falsely illuminate the engine light, among other possibilities.
Basic Step #3
Check the relay. Depending on your system, there may be a cooling fan relay that assists in controlling the fan. Refer to the manufacturer for its location. If the relay appears melted or burnt, it may indicate a problem within the relay and it should be replaced.
TIP: It is advisable to purchase these types of relays from your manufacturer’s dealership, as some aftermarket relays have been found to be defective and can cause serious damage.
Basic Step #4
Check your ECM or PCM. Locate your ECM, which can be found under a seat, under the hood, in the trunk, mounted to the firewall, under the dash, in a fender, or mounted to the floor, depending on the make and model of your vehicle. Inspect the ECM for water damage or corrosion, as this may indicate a problem. Beyond this point, professional assistance may be required.
