P0493: Fan Overspeed | Causes and fixes

Two kinds of cooling fan carry these codes: electric fans switched by relays or driven by a PWM/LIN fan module with speed feedback, and engine-driven fans with an electronically controlled viscous clutch, whose speed a Hall sensor reports – GM calls them EV fans, meaning electro-viscous, not electric vehicle. P0493 is documented only on GM petrol engines of 2004–06 with a viscous fan: the measured fan speed exceeds a limit that is hardly physically possible (about 6400 rpm), so it is effectively a plausibility check of the speed signal or a seized clutch at high engine speed. Two counts set it, with the warning lamp on the first trip – unlike P0495, which needs two trips. Ford, FCA and GM from 2014 were not found to use it.

Medium severity. Can I keep driving?Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

Symptoms

Check engine light on (first trip)
Loud fan roar at higher revs
Higher consumption, slightly less power

Most likely causes

Viscous clutch seized – fan runs rigidly with the belt drive
Interference or faulty signal from the fan speed sensor
Clutch solenoid or its control stuck at fully engaged
Engine module or software

What to check, in order

Start with the simplest. You can tick off each step.

With the engine cold, check the coolant level; never do this when the system is hot
Check the actual temperature in live data
Make sure the fan comes on when it should
Check the thermostat and connector
Measure the sensor and replace it if its readings do not make sense

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P0493 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
4: Emissions
93: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0493?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P0493?

The most common causes are: viscous clutch seized – fan runs rigidly with the belt drive; interference or faulty signal from the fan speed sensor; clutch solenoid or its control stuck at fully engaged.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.