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

P20E9

Reductant Pressure Too High

Manufacturer-specific variant of the reductant over-pressure condition. The pressure exceeds the upper threshold during a defined operating window; on some platforms used in addition to P20E2 to flag a different test path.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / E9

Possible causes

  • Return line blocked or frozen high
  • Pressure sensor reads high 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: medium
  • DIY: shop recommended
  • Estimated cost: 250–1500 €
  • Estimated time: 1–4 h
  • Component: reductant pump
  • Component: reductant pressure sensor
  • MIL / check engine light
  • emissions-relevant
  • drive cycle required

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