P231ACylinder 7 Air-Fuel Ratio Imbalance - Adjustment At Limit During Balance
- 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
- P231A takes the series to cylinder 7; since P2310 to P2319 are ignition coil codes, the versions for cylinders 7 to 12 start at P231A. Only engines with eight or more cylinders can set it. Mercedes-Benz documents it for the 2022 to 2024 SL with the AMG M177 V8 (LI07.61-P-077382): the ME control unit reports irregular mixture formation at cylinder 7 and disables the injector quantity adjustment. The remedy is new ME software; if the latest version is already installed and P231A00 is still present, Mercedes asks for a technical case to be opened instead of parts being replaced. On other engines the causes match smaller ones: injector 7, an intake leak at that port, valve sealing. P21A2 and P0307 cover the same cylinder; the MIL is on.
- What you may notice
- Check engine light on
- Rough idle, possibly misfire on cylinder 7
- Higher fuel consumption or exhaust smell
- Likely causes
- LikelyInjector of cylinder 7 delivering too much or too little (deposits, wear)
- PossibleAir leak at the intake port or injector seal of cylinder 7
- PossibleValve of cylinder 7 not sealing (worn seat or guide), low compression
- PossibleME engine software (Mercedes M177, LI07.61-P-077382)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €0 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.