Powertrain, generic · Auxiliary emission controls

P0493 Fan Overspeed

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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.

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

Symptoms

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

Repair estimate

DifficultyMediumDIY possible
Parts and labour€150–600
Time1–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fan clutchfan speed sensorengine control module

Related codes

P0495P0494P0483P0526P0527

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.