P2C65O2 Sensor Out of Range During Deceleration Bank 1 Sensor 3
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- MIL on, usually without noticeable driving change
- Possibly stored together with other sensor 3 or NOx sensor codes
- Likely causes
- LikelyThird exhaust sensor aged or drifting (wrong value in fresh air)
- PossibleExhaust leak ahead of sensor 3 distorting the overrun reading
- PossibleDamaged sensor wiring or chafed engine harness (GM 3.0L LM2)
- RareLeaking injector or model error disturbing the comparison in overrun
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.