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

P20F1

SCR NOx Pre-Catalyst Over Temperature (Bank 2)

A temperature sensor at the SCR catalyst on bank 2 reports a value above the safe limit — sustained over-temperature can sinter the SCR washcoat and destroy NOx conversion.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / F1

Possible causes

  • Runaway regeneration upstream high

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: 200–4000 €
  • Estimated time: 1.5–8 h
  • Component: scr pre catalyst
  • Component: exhaust temperature sensor
  • 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