Powertrain, generic (extended)

P239E O2 Sensor Out of Range During Deceleration (Bank 1 Sensor 2) - Duplicate Listing of P232F

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P239E carries in common code lists exactly the same wording as P232F: a downstream oxygen sensor on bank 1 reading outside its expected window while fuel is cut on deceleration. No manufacturer, OBD summary or service bulletin on record uses P239E, and no source gives it a meaning of its own. The documented version is P232F, which GM applies to the 2023 6.6L L5P Duramax, comparing sensor 2 with sensor 1 in overrun (window +3.01 to −3.18 %, Type B). P239E is therefore best treated as a duplicate listing. Should a scan tool show it, read the maker's own code definition and freeze-frame data, then test the rear sensor as for P232F; CARB requires a rich-to-lean check of rear sensors during fuel shut-off.

Likely causes

Scan tool code table showing the duplicate number instead of the maker's code
Aged or drifting rear oxygen sensor on bank 1
Exhaust leak ahead of the rear sensor

Symptoms

  • MIL on without noticeable driving change
  • Code text in the scan tool contradicts the manufacturer's documentation

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–300
Time0.3–1.5 h

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

Parts involved

oxygen sensor b1s2

Related codes

P232FP239FP2379

References: gsi.ext.gm.com, law.cornell.edu.