OBD-II code · Powertrain (generic, extended)
P209D Reductant Injection Air Pressure Sensor B Circuit High
The reductant injection air-pressure sensor B reads above its upper plausibility limit — open signal line or short to B+.
Is it safe to drive with P209D?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOpen signal line
- Less likelyConnector pins corroded - high contact resistance
- Less likelySupply wire pinched against B+ source
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)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.7–2 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Air Pressure Sensor
Related codes
- P2040Reductant Injection Air Pressure Sensor A Circuit High
- P209AReductant Injection Air Pressure Sensor B Circuit
- P209BReductant Injection Air Pressure Sensor B Circuit Range/Performance
- P209CReductant Injection Air Pressure Sensor B Circuit Low
- P209EReductant Injection Air Pressure Sensor A/B Correlation
- P209FReductant Tank Heater Control Circuit Performance
- P20A0Reductant Purge Control Valve A Circuit/Open
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.