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

P202F

Reductant/Regeneration Supply Control Circuit Range/Performance

The control line that gates the DEF supply pump or the regeneration heating circuit does not respond as commanded — duty cycle, current draw, or response time off-spec.

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

Possible causes

  • Supply relay aged or pitted contacts high
  • Supply pump motor brushes worn medium
  • Sensor element aged beyond calibration window low

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: medium
  • DIY: shop recommended
  • Estimated cost: 120–800 €
  • Estimated time: 1–3 h
  • Component: reductant supply pump
  • Component: reductant supply relay
  • 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