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

P20FE

Reductant Metering Unit 1 Performance

The first DEF metering unit (the integrated module that combines pump, filter, level sensor, and dosing valve) is electrically OK but does not deliver the expected pressure or flow during operation.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / FE

Possible causes

  • Metering unit aged or partially clogged high

Symptoms

  • Check engine light or NOx warning on
  • AdBlue/DEF level or quality warning
  • Possible no-start countdown after ignore period
  • Failed emissions inspection (NOx)

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 400–3000 €
  • Estimated time: 1.5–5 h
  • Component: reductant metering unit
  • MIL / check engine light
  • emissions-relevant
  • limp mode possible

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