OBD-II Trouble Code Technical Description
Excessive Fan Speed
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles (Chevrolet, Buick, Peugeot, Toyota, Citroen, Dodge, BMW Honda, Acura, Ford, Dodge, etc.). Although generic, the specific repair steps may vary depending on make/model.
The fan referred to in these codes is the cooling fan. Typically, the fan is mounted on the radiator. Its purpose is to cool down the coolant in the radiator and help regulate engine temperature.
The engine control module (ECM) or power train control module (PCM) monitors and controls various sensors to monitor and regulate the engine’s temperature. The ECM activates the fan when the engine temperature rises (e.g. idling in traffic) and deactivates it when there is sufficient airflow to keep temperatures down (i.e. cruising down the highway).
While monitoring the cooling fan, the ECM has detected that the fan is spinning at an excessive speed. If the cooling fan is spinning beyond or below the manufacturer’s set parameters, the engine light or malfunction indicator lamp (MIL) will be illuminated by the ECM.
Related engine cooling fan diagnostic codes:
Symptoms
Symptoms of a P0493 engine code may include:
Potential Causes
Typically, the causes for this code to 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. Start by opening the hood and locating the radiator/fan assembly. In most cases, it will be mounted towards the front of the vehicle, directly in front of the engine. Keep in mind that there are various styles and setups for cooling fans. Some are mounted directly on the radiator itself, while others are belt-driven by the engine. Identify the style of your particular cooling fan. Once located, inspect the fan(s) and blades for any damage. It is a good idea to lightly shake one of the fan blades to check for any play in the bearings. Depending on the style and amount of play present, you may need to replace the fan assembly. 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 certain codes. If everything checks out, continue.
TIP: Sometimes aftermarket shrouds do not fit perfectly, causing the fan to rub on parts of the shroud and resulting in a low-speed condition. Spin the fan by hand with the engine off and cold. The fan should spin freely in the shroud (you may have to remove the belt for the belt-driven version).
Basic Step #2
Check the connector. First, ensure that the battery is disconnected before performing any repairs or tests on the electrical system. Follow the harness coming out of the cooling fan until you find its connector. Once located, inspect it for overheating/melting or corrosion. Disconnect the connector and inspect the pins inside. Any corroded or bent pins must be repaired or replaced. Typically, any damage to the connector means it needs to be replaced. If everything looks good, continue.
TIP: Ensure that you have a healthy electrical system. Always be aware that if you have a weak battery or a problem with your charging system, the ECM may falsely illuminate the engine light, among numerous other possibilities.
Basic Tip #3
Check the relay. Depending on your system, you may have a cooling fan relay that assists in controlling your fan. Refer to the manufacturer for its location. If the relay appears melted or burnt, this may indicate a problem within the relay and it should be replaced.
TIP: It is advisable to purchase these types of relays at your manufacturer’s dealership, as I have found some defective aftermarket relays that have caused serious damage.
Basic Step #4
Check your ECM or PCM. Locate your ECM. The location heavily depends on the make and model of your vehicle. You may find the ECM under a seat, under the hood, in the trunk, mounted to the firewall, under the dash, in a fender, or mounted to the floor somewhere. Once located, inspect it for water damage or corrosion, as this may indicate a problem. Qualified assistance would be needed beyond this point.
