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.
Affected components
- Nh3 sensor
- Sensor eeprom
Common causes
- High likelihood: New sensor installed but not coded/learned to the ECM
- Medium likelihood: Corrupted calibration memory after voltage drop
- Low likelihood: Module software outdated, reflash may resolve
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.