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

P24EC

NH3 Sensor Supply Voltage Circuit High

The NH3 slip sensor supply voltage rises above the upper limit. Either the supply is shorted to battery voltage or an internal regulator in the dosing module has failed open. The sensor electronics may be damaged if the condition persists, so the ECM disables the input.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number4 / EC

Possible causes

  • Supply line shorted to battery voltage high
  • Failed voltage regulator in the dosing module medium
  • Connector pins corroded - high contact resistance low

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 120–700 €
  • Estimated time: 0.5–2 h
  • Component: nh3 sensor
  • Component: supply wiring
  • Component: dosing module
  • 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