P0493Fan Overspeed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- 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.
- What you may notice
- Check engine light on (first trip)
- Loud fan roar at higher revs
- Higher consumption, slightly less power
- Likely causes
- LikelyViscous clutch seized – fan runs rigidly with the belt drive
- PossibleInterference or faulty signal from the fan speed sensor
- PossibleClutch solenoid or its control stuck at fully engaged
- RareEngine module or software
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €150 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.