Powertrain
generic / SAE
P22A5
NOx Sensor Heater Control Circuit High (Bank 1 Sensor 2)
NOx heater drive line on bank 2 stuck high — short to B+. The sensor heater warms the element to operating temperature (~600 °C); without it the lambda sensor stays inactive in closed loop and the ECM cannot trim mixture.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number2 / A5
Possible causes
- Short to B+ high
- Connector pins corroded - high contact resistance low
- Supply wire pinched against B+ source low
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 200–1200 €
- Estimated time: 1–3 h
- Component: nox sensor
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012