Powertrain, generic (extended)

P24ED NH3 Sensor Calibration Memory

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Every NH3 sensor leaves the factory with individual correction values for offset and gain stored in its own electronics. P24ED means this memory fails its integrity check, for instance a checksum mismatch or unreadable data, so the module cannot convert the raw probe signal into a trustworthy ammonia value. The fix is normally a new sensor; wiring rarely plays a part. It differs from the engine software choice in Ram bulletin 18-042-20, where 2014 Ram 3500 to 5500 cab chassis trucks receive one controller calibration with the ammonia sensor and another without it. No manufacturer documents P24ED publicly. CARB demands that heavy-duty sensors be checked for faults. P24EE covers the sensor processor.

Likely causes

Calibration data in the sensor module corrupted
Power loss while the module was writing data

Symptoms

  • Check engine light on
  • No valid ammonia value although wiring tests pass

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€300–1,400
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

nh3 sensorsensor eeprom

Related codes

P24EEP24E1

References: law.cornell.edu, static.nhtsa.gov.