P2BADNOx Exceedence - Root Cause Unknown
- 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
- P2BAD is the catch-all of the series: NOx after the SCR is measured too high, yet none of the specific causes from P2BA6 to P2BAC can be pinned down. GM uses it on the 2014 Duramax 6.6 L LML as Exhaust NOx Concentration High - Unknown Reason: the measured SCR efficiency, minus an offset-corrected model value, is filtered over time and fails once the difference drops below zero, with both NOx sensors active for over 60 s; Type A. GM PIP5007 notes that from 2012 this code takes over from P20EE/P207F as the diagnostic path when the DIC reports poor fluid quality. Nissan lists it as NOx Concentration Exceeded for the 2016 Titan XD with the Cummins 5.0 L and fixes it by reflashing the ECM. Diagnosis starts with DEF quality, dosing and sensors.
- What you may notice
- Exhaust fluid quality poor or emission warning
- MIL on after the first failed run
- Speed limit countdown if the condition persists
- Likely causes
- LikelyPoor DEF quality or partly blocked dosing without a specific code
- PossibleAged or deposit-covered SCR catalyst
- PossibleUpstream or downstream NOx sensor drifting
- PossibleEngine control software needing an update (Nissan Titan XD)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €0 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.