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

P04CD

Fuel Fill Door Open Request Sensor or Switch Stuck On

The open-request switch is stuck in the active state - the ECU continuously reads a request to open the fuel fill door. Either the switch is mechanically held closed or the line is shorted to its active level.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number4 / CD

Possible causes

  • Switch contact mechanically stuck closed high
  • Carbon or debris buildup preventing free movement low
  • Component wear with age - mechanical play low

Inspection / repair

  • Difficulty: easy
  • DIY: possible
  • Estimated cost: 60–220 €
  • Estimated time: 0.4–1 h
  • Component: fuel fill door request switch

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