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

P202D

Reductant Leakage

A leak has been detected in the DEF (urea) supply system — usually by a pressure-decay test after pump shutdown, or by visible crystallisation around fittings.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / 2D

Possible causes

  • Cracked DEF line or fitting high
  • Pump seal leaking medium
  • Injector mounting seal leaking medium

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: 120–1500 €
  • Estimated time: 1–4 h
  • Component: reductant supply line
  • Component: reductant pump
  • Component: reductant injection valve
  • 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