OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P0495

Fan 1 Overspeed

The cooling fan is rotating faster than the commanded speed. The control unit measures the fan tachometer feedback against the requested duty cycle and finds it well above the expected band - typically a stuck-open relay, a shorted PWM line driving the fan to full power, or a feedback line that misreports speed.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number4 / 95

Possible causes

  • Fan 1 relay welded closed high
  • PWM line shorted to supply medium

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 80–400 €
  • Estimated time: 0.6–1.8 h
  • Component: cooling fan 1
  • Component: fan relay 1
  • MIL / check engine light

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication