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

P20D8

Exhaust Aftertreatment Fuel Supply Control Performance

Aftertreatment fuel supply is electrically OK but does not deliver the commanded pressure or flow during regeneration — weak pump or partial blockage.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / D8

Possible causes

  • Pump weak — flow or pressure below threshold high

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 150–1200 €
  • Estimated time: 0.7–3.5 h
  • Component: aftertreatment fuel pump
  • 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