P2BAANOx Exceedence - Low Reagent Consumption
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2BAA means less reagent is actually reaching the exhaust than the dosing strategy asks for, so NOx stays too high. EU Annex XVI sets the frame: actual and demanded consumption are compared, and a gap above 50 % over 30 minutes triggers the warning. GM uses P2BAA on its diesel engines as Reductant Delivery Performance, Type A after one trip: 14OBDG04 checks a filtered DEF pressure drop against 365 kPa, while 16OBDG04 and 18OBDG04 compare the pressure drop after each injection with an expected value derived from pump duty. GM bulletin 25-NA-042 cures false P2BAA on 2023 Silverado 4500HD to 6500HD (L5D) with an ECM update. Neighbours: P2BA8 for stopped dosing, P2BA7 for an empty tank; drivers see a service emission system message.
- What you may notice
- Service emission or exhaust fluid system message
- MIL on after one trip
- DEF level falls more slowly than usual
- Likely causes
- LikelyPartially blocked DEF injector delivering too little
- PossibleWeak DEF pump or clogged pump filter
- PossibleCalibration error setting the code without a fault (GM 25-NA-042)
- RareLeak in the pressure line returning fluid before the injector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €0 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.