P0495Fan 1 Overspeed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- 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. 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.
- What you may notice
- Check engine light on
- Loud fan roar even with a cold engine or at idle
- Slightly higher consumption, longer warm-up
- Likely causes
- LikelyViscous clutch does not release (gummed, overfilled, seized)
- PossibleClutch solenoid or its control stuck open (short to positive, valve sticking)
- PossibleWrong speed signal (sensor, wiring, interference)
- RareElectric fan: module runs uncontrolled at full speed or relay sticking
- 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 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.