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

P04C1

Fuel Fill Door Unlock Control Circuit Low

Same as P04BD on the unlock side. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number4 / C1

Possible causes

  • Control line shorted to ground high
  • Connector pins corroded - high contact resistance low
  • Harness chafing through insulation low

Inspection / repair

  • Difficulty: easy
  • DIY: possible
  • Estimated cost: 80–280 €
  • Estimated time: 0.5–1.4 h
  • Component: fuel fill door unlock actuator

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