OBD-II code · Powertrain (generic, extended)
P20AB Reductant Injection Air Pressure Control Valve Stuck Closed
Reductant air-pressure control valve mechanically stuck closed — air supply blocked, dosing fails.
Is it safe to drive with P20AB?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyValve stuck closed
- Less likelyCarbon or debris buildup preventing free movement
- Less likelyComponent wear with age - mechanical play
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
- 0.7–3 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Air Pressure Control Valve
Related codes
- P20A6Reductant Injection Air Pressure Control Valve Circuit/Open
- P20A8Reductant Injection Air Pressure Control Valve Circuit Low
- P20A9Reductant Injection Air Pressure Control Valve Circuit High
- P20AAReductant Injection Air Pressure Control Valve Stuck Open
- P20ACReductant Metering Unit Temperature Sensor Circuit
- P20ADReductant Metering Unit Temperature Sensor Circuit Range/Performance
- P20AEReductant Metering Unit Temperature Sensor Circuit Low
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.