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.
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
- Loud fan roar even with a cold engine or at idle
- Slightly higher consumption, longer warm-up
Most 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
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P0495 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 4: Emissions
- 95: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0495?
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 P0495?
The most common causes are: 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).
Related codes
- P0493Fan Overspeed
- P0494Fan 1 Underspeed
- P0483Fan Rationality Check
- P0526Fan Speed Sensor Circuit
- P0529Fan Speed Sensor Circuit Intermittent
- P0480Fan 1 Control Circuit
Sources
- gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
- gsi.ext.gm.com: 16OBDG04 Engine Diagnostics
- gsi.ext.gm.com: 2005file2
- gsi.ext.gm.com: 20OBDG03A Diagnostics
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.