Powertrain
generic / SAE
P231A
Cylinder 7 Air-Fuel Ratio Imbalance Adjustment At Limit During Balance
The ECU continuously trims individual cylinders to equalise air-fuel ratio across the bank using ion-current or per-cylinder lambda feedback. For cylinder 7 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.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number3 / 1A
Possible causes
- Fuel injector for cylinder 7 has drifted in flow rate high
- Reduced compression on cylinder 7 medium
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 200–1200 €
- Estimated time: 1–4 h
- Component: fuel injector cyl 7
- Component: intake manifold
- Component: cylinder compression
- Component: per cylinder lambda strategy
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012