Powertrain, generic · Auxiliary emission controls

P0495 Fan 1 Overspeed

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
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. P0495 mainly concerns viscous fans: with the fan commanded off it turns faster than the permitted drag speed, so the clutch does not release. GM thresholds: Duramax 2016 above 1500 rpm, Duramax 2018 above a calculated drag speed, petrol SUVs of 2004–05 above 1600 rpm without command – all with the warning lamp after two trips; Ford's 6.7-litre Super Duty uses it the same way. On GM's 2020 2.0-litre turbo with a LIN electric fan it means a reported speed above 2900 rpm.

Likely causes

Viscous clutch does not release (gummed, overfilled, seized)
Clutch solenoid or its control stuck open (short to positive, valve sticking)
Wrong speed signal (sensor, wiring, interference)
Electric fan: module runs uncontrolled at full speed or relay sticking

Symptoms

  • Check engine light on
  • Loud fan roar even with a cold engine or at idle
  • Slightly higher consumption, longer warm-up

Repair estimate

DifficultyMediumDIY possible
Parts and labour€150–800
Time1–3 h

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

Parts involved

fan clutchcooling fan 1fan speed sensorengine control module

Related codes

P0493P0494P0483P0526P0529P0480

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