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

P2577

Direct Ozone Reduction Catalyst Efficiency Below Threshold

The DOR catalyst no longer reduces tropospheric ozone with the required efficiency, based on the deterioration sensor and operating-time model. Coating worn off the radiator surface, contaminated by road salt and grime, or thermally aged after many heat cycles. Replacing the affected radiator/coating restores function.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / 77

Possible causes

  • DOR coating worn off the radiator high
  • Coating contaminated by salt and grime medium

Symptoms

  • Check engine light on
  • Failed emissions inspection
  • Possibly slightly increased fuel consumption
  • Sulfur (rotten egg) smell from exhaust under load

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 400–1800 €
  • Estimated time: 1.5–4 h
  • Component: dor catalyst
  • 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