P231B: Cylinder 8 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
Standardized SAE J2012 code · P23xx — Ignition system and misfire
What does P231B mean?
The ECU continuously trims individual cylinders to equalise air-fuel ratio across the bank using ion-current or per-cylinder lambda feedback. For cylinder 8 the per-cylinder fuel correction has hit its software-side maximum or minimum without restoring balance, indicating the underlying mechanical or fuelling deviation is too large to compensate.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Common causes
- High Fuel injector for cylinder 8 has drifted in flow rate
- Medium Reduced compression on cylinder 8
Likelihood is a general estimate across vehicles; your make and model may differ.
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Describe your P231B problemRelated codes
- P230A Cylinder 1 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P230B Cylinder 2 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P230C Cylinder 3 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P230D Cylinder 4 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P230E Cylinder 5 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P230F Cylinder 6 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P231A Cylinder 7 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P231C Cylinder 9 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P231D Cylinder 10 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P231E Cylinder 11 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
- P231F Cylinder 12 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance