Powertrain
generic / SAE
P24E7
NH3 Sensor Heater Circuit Low
The heater control circuit of the ammonia (NH3) slip sensor reads below the expected voltage range. Either the wiring is shorted to ground or the heater driver in the SCR/dosing module is stuck low. The sensor element never warms up, NH3 readings stay invalid and the SCR strategy falls back to open-loop dosing.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number4 / E7
Possible causes
- Heater control wire shorted to ground high
- Internal short across the heater element medium
- Low-side driver pulled down in the control module low
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 180–900 €
- Estimated time: 0.6–2 h
- Component: nh3 sensor heater
- Component: heater driver
- Component: sensor wiring
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012