P231E code meaning
Cylinder 11 Air-Fuel Ratio Imbalance - Adjustment At Limit During Balance
Powertrain system Generic code P23xx codes Check engine light
What P231E means
P231E belongs to cylinder 11 and can only come from twelve-cylinder engines, V12 or W12. The per-cylinder fuel trim for cylinder 11 sits at its limit during balancing. There is no public manufacturer description and no NHTSA bulletin. On such engines six cylinders share each bank, so one deviating cylinder shifts the bank sensor signal only slightly; that is one reason CARB accepts a bank or misfire code where a single cylinder cannot be resolved. Mercedes' M177 bulletin for the cylinder 7 code of the same series shows that a software update can be the real remedy. In the workshop, compare the trim values and misfire counts of cylinder 11 (P0311, P21A6) with its neighbours before the injector is replaced.
P231E 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 P231E
- Check engine light on
- Rough idle, possibly misfire on cylinder 11
- Higher fuel consumption or exhaust smell
Common causes of P231E
- Most likelyInjector of cylinder 11 delivering too much or too little (deposits, wear)
- PossibleAir leak at the intake port or injector seal of cylinder 11
- PossibleValve of cylinder 11 not sealing (worn seat or guide), low compression
- Less likelyPoor contact at the connector of injector 11
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injector cyl 11Intake manifoldCylinder compression
What each part of P231E 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. |
| 1E | The exact fault in that area. |
What to do next
- Note P231E 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 P231E
What does P231E mean?
P231E means "Cylinder 11 Air-Fuel Ratio Imbalance - Adjustment At Limit During Balance". P231E belongs to cylinder 11 and can only come from twelve-cylinder engines, V12 or W12. It is a generic code, so it means the same on every make.
Is it safe to drive with P231E?
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 P231E fail an emissions test?
Yes, it can. P231E 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 P231E to fix?
Difficulty: medium. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will P231E 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.