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P0493 OBD-II Trouble Code: Fan Overspeed

Check Engine Light

P0493 trouble code definition

A P0493 trouble code is related to a vehicle’s electric cooling fan, or auxiliary fan, that helps the radiator maintain engine coolant temperatures that are within the manufacturer’s parameters. Typically, this fan is also triggered by a vehicle’s HVAC system.

What the P0493 code means

P0493 is an OBD-II generic code for a voltage problem with the electric cooling fan control system in that the signal being sent to the engine computer is incorrect. This either means there is a bad ground or the fan isn’t working.

What causes the P0493 code?

There could be a variety of causes for a P0493, but the most common culprits are:

  • Faulty electric fan motor
  • Faulty electric fan relay
  • Faulty wiring and electrical connectors for the fan
  • Faulty engine coolant temperature sensor
  • Blown electric fan fuse

What are the symptoms of the P0493 code?

Other than A Check Engine Light, there shouldn’t be any severely adverse driving conditions caused by a P0493. However, because the electric cooling fan is used to keep coolant temperatures below an overheating threshold, you may find your vehicle running hotter than normal in conditions such as stop-and-go traffic. The fan is also used frequently to accelerate and maintain cooling of the air conditioning, which may be diminished if the fan is inoperable.

How does a mechanic diagnose the P0493 code?

Your mechanic will start at the easiest first - giving a visual inspection of the fan, its wiring and electrical connectors, associated fuses and the control relay. If nothing looks to need repairs, they will then trigger the fan to power by either jumping the relay, sending 12 volts directly to the fan, or triggering it via the air conditioning. If and under what conditions the fan turns on will help determine the route cause of the problem.

For example, if the fan turns on when the relay is jumped but does not when the air conditioning is triggered, chances are high the relay is bad. If the fan doesn’t turn on at all, the motor is bad and will need to be replaced. The key with a P0493 is first confirming if the fan motor is good and then moving on to the next most common cause, typically the relay.

Common mistakes when diagnosing the P0493 code

Rushing to replace parts like the fan and the relay can become costly, so it really pays to test each component of the vehicle’s electric cooling system.

How serious is the P0493 code?

A P0493 shouldn’t cause serious issues but if you have a code, you’ll want to be on high alert in slow driving conditions with high ambient temperatures. While it’s unlikely that a vehicle will overheat severely without an electric cooling fan, a hot-running engine will not perform as well as normal.

What repairs can fix the P0493 code?

The most common repairs for a P0493 are as follows:

Additional comments for consideration regarding the P0493 code

If you’re dealing with a P0493 on a used vehicle with unknown history, you’ll want to also make sure you’re not dealing with someone else’s shadetree work. Having personally triggered this code by modifying a vehicle’s factory fan to a toggle switch, it can take a lot of research and soldering to make sure it goes away with a modification.

Need help with a P0493 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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