OBD-II code · Powertrain (generic, extended)
P2351 Cylinder 9 Combustion Performance
The closed-loop combustion controller reports that combustion performance on cylinder 9 is below the calibrated quality metric. Computed from the cylinder pressure trace — IMEP (indicated mean effective pressure), CA50 (50% mass burnt angle) or peak pressure deviates from the model.
Is it safe to drive with P2351?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyMean effective pressure outside model
- PossibleInjector flow has drifted
- Less likelyGateway module routing CAN messages incorrectly
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1.5–6 h
- Emissions test
- Likely to fail
- Parts involved
- Cylinder 9 Combustion, Cylinder Pressure Sensor 9, Fuel Injector Cyl 9
Related codes
- P039ECylinder 1 Combustion Performance
- P03A8Cylinder 2 Combustion Performance
- P03B2Cylinder 3 Combustion Performance
- P03BCCylinder 4 Combustion Performance
- P03C6Cylinder 5 Combustion Performance
- P03D0Cylinder 6 Combustion Performance
- P03DACylinder 7 Combustion Performance
- P03E4Cylinder 8 Combustion Performance
- P235BCylinder 10 Combustion Performance
- P2365Cylinder 11 Combustion Performance
- P236FCylinder 12 Combustion Performance
- P234ECylinder 9 Pressure Too High
- P234FCylinder 9 Pressure Variation Low
- P2350Cylinder 9 Pressure Variation High
- P2352Cylinder 10 Pressure Sensor Circuit
- P2353Cylinder 10 Pressure Sensor Circuit Range/Performance
- P2354Cylinder 10 Pressure Sensor Circuit Low
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.