Powertrain, generic (extended)

P239F O2 Sensor Out of Range During Deceleration (Bank 2 Sensor 2) - Duplicate Listing of P2379

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P239F appears in code lists with the identical title already given to P2379: the post-catalyst oxygen sensor of bank 2 is out of range while the injectors are switched off on a closed throttle. Neither code has a published manufacturer application; the only documented member of this deceleration check is GM's bank 1 code P232F on the single-bank 2023 L5P diesel, so a second bank never occurs there. No source assigns P239F a separate meaning, which makes it a duplicate listing of P2379. If it is ever read out, the manufacturer's code text decides; diagnosis would follow the bank 2 rear sensor: look for exhaust leaks ahead of it, check wiring and compare its overrun reading with the front sensor. CARB requires such fuel-cut checks for rear sensors.

Likely causes

Scan tool listing the duplicate number for a maker-specific fault
Aged rear oxygen sensor on bank 2
Air leak in the bank 2 exhaust ahead of the sensor

Symptoms

  • MIL on, engine runs normally
  • Catalyst monitor may not complete

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 b2s2

Related codes

P2379P239EP232F

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