Powertrain, generic (extended)

P2C65 O2 Sensor Out of Range During Deceleration Bank 1 Sensor 3

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2C65 is the overrun plausibility check for the third oxygen sensor of bank 1: with fuel cut on deceleration the exhaust is close to fresh air, so the reading must land inside a known window. GM's 3.0L Duramax runs this test for sensor 1 under P2297, where table 25OBDG04B compares the measured O2 value with an estimate in overrun and flags a gap above 4 or below -3.25 percent (Type B). For sensor 3, NOx sensor 3 behind the second catalyst, GM publishes no threshold, but PIT5751C and bulletin 21-NA-149 list P2C65 together with P2C63/P2C64 on 2020-21 trucks and SUVs with the 3.0L LM2, where a chafed engine harness was the cause. CARB accepts a check during fuel shut-off where full rear-sensor monitoring is not feasible. The sensor 2 code is P232F, sensor 1 P2297.

Likely causes

Third exhaust sensor aged or drifting (wrong value in fresh air)
Exhaust leak ahead of sensor 3 distorting the overrun reading
Damaged sensor wiring or chafed engine harness (GM 3.0L LM2)
Leaking injector or model error disturbing the comparison in overrun

Symptoms

  • MIL on, usually without noticeable driving change
  • Possibly stored together with other sensor 3 or NOx sensor codes

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–600
Time0.3–2 h

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

Parts involved

oxygen sensor b1s3nox sensoroxygen sensor wiring

Related codes

P2C63P2C64P232FP2297P23AD

References: static.nhtsa.gov, static.nhtsa.gov, gsi.ext.gm.com, law.cornell.edu.