Powertrain
generic / SAE
P24E5
NH3 Sensor Circuit Intermittent/Erratic
The ammonia (NH3) slip sensor downstream of the SCR catalyst delivers an intermittent or erratic signal. The ECM expects a smooth voltage proportional to ammonia concentration in the tailpipe — sudden jumps, dropouts or noise mean the wiring, connector or sensing element is failing. Used to close-loop the AdBlue/DEF dosing strategy.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number4 / E5
Possible causes
- Corroded or loose sensor connector high
- Chafed or vibrating harness near the exhaust medium
- Aged ceramic sensor element drifting under heat cycles medium
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 180–900 €
- Estimated time: 0.6–2 h
- Component: nh3 sensor
- Component: sensor wiring
- Component: sensor connector
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012