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

P24EE

NH3 Sensor Processor Performance

The microcontroller inside the smart NH3 slip sensor reports an internal performance fault — failed self-test, watchdog reset, or out-of-range plausibility checks. The sensor cannot guarantee its output value, the ECM marks the channel invalid and disables SCR closed-loop control on this branch.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number4 / EE

Possible causes

  • Internal processor or firmware fault high
  • Brown-out from supply voltage dips medium
  • Module software outdated, reflash may resolve low

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 200–900 €
  • Estimated time: 0.5–2 h
  • Component: nh3 sensor
  • Component: sensor microcontroller
  • 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