NH3 Sensor Supply Voltage Circuit
The supply rail that powers the NH3 slip sensor electronics (typically 5 V or 12 V from the dosing/SCR module) is out of tolerance. Without a stable supply the sensor cannot deliver a valid ammonia reading, and the ECM disables the closed-loop SCR strategy.
Affected components
- Nh3 sensor
- Supply wiring
- Dosing module
Common causes
- High likelihood: Open or shorted supply wire
- Medium likelihood: Failing supply rail inside the dosing module
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.