OBD-II code · Powertrain (generic)
P039E Cylinder 1 Combustion Performance
The closed-loop combustion controller reports that combustion performance on cylinder 1 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 P039E?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyInjector flow rate drift
- PossibleLow compression
- Less likelyGateway module routing CAN messages incorrectly
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–6 h
- Emissions test
- Likely to fail
- Parts involved
- Cylinder Pressure Sensor, Fuel Injector
Related codes
- P0395Cylinder 1 Pressure Sensor Circuit
- 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
- P2351Cylinder 9 Combustion Performance
- P235BCylinder 10 Combustion Performance
- P2365Cylinder 11 Combustion Performance
- P236FCylinder 12 Combustion Performance
- P039BCylinder 1 Pressure Too High
- P039CCylinder 1 Pressure Variation Low
- P039DCylinder 1 Pressure Variation High
- P039FCylinder 2 Pressure Sensor Circuit
- P03A0Cylinder 2 Pressure Sensor Circuit Range/Performance
- P03A1Cylinder 2 Pressure Sensor Circuit Low
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.