Powertrain
generic / SAE
P24ED
NH3 Sensor Calibration Memory
The NH3 slip sensor stores its individual calibration coefficients in non-volatile memory (EEPROM/flash). The ECM cannot read valid calibration values — either checksum fails, the memory is empty after replacement, or communication with the sensor electronics is broken. Without the trim values the raw ammonia reading is unreliable.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number4 / ED
Possible causes
- New sensor installed but not coded/learned to the ECM high
- Corrupted calibration memory after voltage drop medium
- Module software outdated, reflash may resolve low
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 80–600 €
- Estimated time: 0.3–1.5 h
- Component: nh3 sensor
- Component: sensor eeprom
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012