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

P20DF

Exhaust Aftertreatment Fuel Pressure Sensor Circuit Low

Aftertreatment fuel-pressure sensor below lower plausibility — short to ground. 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
GroupP2
Range / number– / DF

Possible causes

  • Short to ground high
  • Connector pins corroded - high contact resistance low
  • Harness chafing through insulation low

Symptoms

  • Check engine light on
  • Hard start, no start, or stalling under load
  • Power loss especially at high load or rpm
  • Possible long cranking time

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 150–1000 €
  • Estimated time: 0.7–3 h
  • Component: aftertreatment fuel pressure sensor
  • MIL / check engine light
  • emissions-relevant

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