P231D code meaning
Cylinder 10 Air-Fuel Ratio Imbalance - Adjustment At Limit During Balance
Powertrain system Generic code P23xx codes Check engine light
What P231D means
P231D is the cylinder 10 code of the balance-limit series. On a V10 it marks the last cylinder, on a V12 one of the inner ones; smaller engines cannot set it. The individual fuel correction for cylinder 10 has reached its end stop while the controller tried to equalise the mixture. No maker publishes a description, and no NHTSA bulletin lists it. The principle is the one Mercedes describes on its M260/M264 four-cylinders as injector quantity adjustment for cylinder balancing, with P1CEF85 when it nears the upper limit, there often caused by worn valve seats. CARB's imbalance monitor (13 CCR 1968.2 (e)(6.2.1)(C)) applies to these engines too. Look at injector 10, the intake runner seal and valve tightness, and check whether P0310 or P21A5 are stored as well.
P231D 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 P231D
- Check engine light on
- Rough idle, possibly misfire on cylinder 10
- Higher fuel consumption or exhaust smell
Common causes of P231D
- Most likelyInjector of cylinder 10 delivering too much or too little (deposits, wear)
- PossibleAir leak at the intake port or injector seal of cylinder 10
- PossibleValve of cylinder 10 not sealing (worn seat or guide), low compression
- Less likelyPoor contact at the connector of injector 10
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injector cyl 10Intake manifoldCylinder compression
What each part of P231D 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. |
| 1D | The exact fault in that area. |
What to do next
- Note P231D 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 P231D
What does P231D mean?
P231D means "Cylinder 10 Air-Fuel Ratio Imbalance - Adjustment At Limit During Balance". P231D is the cylinder 10 code of the balance-limit series. It is a generic code, so it means the same on every make.
Is it safe to drive with P231D?
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 P231D fail an emissions test?
Yes, it can. P231D 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 P231D to fix?
Difficulty: medium. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will P231D 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.