P2C65 code meaning
O2 Sensor Out of Range During Deceleration Bank 1 Sensor 3
Powertrain system Generic code P2Cxx codes Check engine light
What P2C65 means
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.
P2C65 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P2C65
- MIL on, usually without noticeable driving change
- Possibly stored together with other sensor 3 or NOx sensor codes
Common causes of P2C65
- Most 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)
- Less likelyLeaking injector or model error disturbing the comparison in overrun
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Oxygen sensor b1s3Nox sensorOxygen sensor wiring
What each part of P2C65 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| C | Area: hybrid propulsion. |
| 65 | The exact fault in that area. |
What to do next
- Note P2C65 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2C65
What does P2C65 mean?
P2C65 means "O2 Sensor Out of Range During Deceleration Bank 1 Sensor 3". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P2C65?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2C65 fail an emissions test?
Yes, it can. P2C65 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2C65 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P2C65 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.