NH3 Sensor Supply Voltage Circuit Low
The NH3 slip sensor supply voltage drops below the lower limit. Usually a partial short to ground in the supply line, an undersized ground path with high resistance, or an internal supply collapse in the SCR/dosing module. Sensor output is held invalid until the supply recovers.
Affected components
- Nh3 sensor
- Supply wiring
- Dosing module
Common causes
- High likelihood: Supply line shorted to ground
- Medium likelihood: High-resistance ground at the SCR module
- Low likelihood: Connector pins corroded - high contact resistance
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
Related codes
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.