P231FCylinder 12 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
- P231F closes the balance-limit series at cylinder 12, the last cylinder of a twelve-cylinder engine. It says the balancing routine has used up the fuel trim for that cylinder without matching it to the rest. Public manufacturer documentation is missing, and the NHTSA index contains no bulletin naming it. CARB's monitor requirement, and its demand that the stored code identify the cylinder wherever the method allows, apply to these rare engines as well. A V12 has two independent banks, so compare the matching bank code (P219A or P219B) with the misfire counter P0312 and with P21A7 before fitting parts. Mercedes' bulletins for its four-cylinders, where worn valve seats caused balancing faults, are a reminder that the injector is not always the culprit.
- What you may notice
- Check engine light on
- Rough idle, possibly misfire on cylinder 12
- Higher fuel consumption or exhaust smell
- Likely causes
- LikelyInjector of cylinder 12 delivering too much or too little (deposits, wear)
- PossibleAir leak at the intake port or injector seal of cylinder 12
- PossibleValve of cylinder 12 not sealing (worn seat or guide), low compression
- RarePoor contact at the connector of injector 12
- 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.