P231F code meaning
Cylinder 12 Air-Fuel Ratio Imbalance - Adjustment At Limit During Balance
Powertrain system Generic code P23xx codes Check engine light
What P231F means
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.
P231F at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 6 hours
- Clears after repairAfter a drive cycle
Symptoms of P231F
- Check engine light on
- Rough idle, possibly misfire on cylinder 12
- Higher fuel consumption or exhaust smell
Common causes of P231F
- Most 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
- Less likelyPoor contact at the connector of injector 12
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injector cyl 12Intake manifoldCylinder compression
What each part of P231F means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 3 | Area: ignition system or misfire. |
| 1F | The exact fault in that area. |
What to do next
- Note P231F 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 P231F
What does P231F mean?
P231F means "Cylinder 12 Air-Fuel Ratio Imbalance - Adjustment At Limit During Balance". P231F closes the balance-limit series at cylinder 12, the last cylinder of a twelve-cylinder engine. It is a generic code, so it means the same on every make.
Is it safe to drive with P231F?
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 P231F fail an emissions test?
Yes, it can. P231F 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 P231F to fix?
Difficulty: medium. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will P231F 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.