Powertrain, generic (extended)

P2BAB NOx Exceedence - Incorrect EGR Flow

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2BAB attributes excess NOx to exhaust gas recirculation that delivers the wrong amount of gas, so combustion temperature and raw NOx rise. It belongs to the European NOx control rules: Regulation (EU) No 582/2011, Annex XIII, handles tampering-related monitoring through UN Regulation 49 and keeps an EGR valve counter, so an impeded valve leads to warning and inducement. CARB 13 CCR 1968.2 (f)(6.2) separately demands low and high flow detection, normally reported as P0401 and P0402. No maker documents P2BAB publicly; it serves as the emissions link to those EGR flow codes, which point to the actual part. P2BAC is used when EGR is switched off entirely. The driver sees the MIL and, depending on the maker, a NOx warning and later reduced power.

Likely causes

EGR valve sooted up or sticking
EGR cooler or pipe partly blocked
Faulty EGR position sensor or air mass meter distorting flow estimate
Leak in the intake or EGR path

Symptoms

  • MIL on, EGR flow codes stored
  • Rough running or sooting with too much EGR
  • Power reduction possible if not repaired

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€150–1,500
Time1–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

egr valveegr cooler

Related codes

P0400P0401P0402P2BAC

References: legislation.gov.uk, law.cornell.edu.