P231DCylinder 10 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
- 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.
- What you may notice
- Check engine light on
- Rough idle, possibly misfire on cylinder 10
- Higher fuel consumption or exhaust smell
- Likely causes
- 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
- RarePoor contact at the connector of injector 10
- 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.