Powertrain, generic (extended)

P225E NOx Sensor Performance - Signal Biased/Stuck High (Bank 1 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P225E points at the downstream NOx sensor of bank 1, behind the SCR catalyst, reading persistently high. Because that sensor sees what is left after urea dosing, a high value can be a sensor offset or genuine NOx slipping through a weak catalyst, poor DEF or a faulty dosing valve. Volvo and Mack therefore put P225E in the group where either sensor or the aftertreatment itself may be the cause: their replacement guide and bulletin KC-107 require a NOx conversion test or the aftertreatment analysis in PTT before any part is changed, and for P225E they also send technicians to the DEF dosing valve diagnosis. No public bulletin from a passenger car maker covers P225E. P225C is the same fault upstream; P225F is the low-reading downstream case.

Likely causes

Real NOx slip from a weak SCR catalyst, poor DEF quality or a faulty dosing valve
Downstream NOx sensor with a positive offset
Control software that evaluates the sensor incorrectly

Symptoms

  • MIL on, often together with P20EE
  • Increased DEF consumption or DEF quality warnings
  • Power reduction possible if SCR efficiency codes follow

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–2,500
Time1–4 h

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

Parts involved

nox sensor

Related codes

P225FP225CP221AP20EEP229E

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.