Powertrain
generic / SAE
P209C
Reductant Injection Air Pressure Sensor B Circuit Low
The reductant injection air-pressure sensor B reads below its lower plausibility limit — short to ground or sensor internal short.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / 9C
Possible causes
- Short to ground high
- Connector pins corroded - high contact resistance low
- Harness chafing through insulation 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: 80–500 €
- Estimated time: 0.7–2 h
- Component: reductant air pressure sensor
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012