P21A1
Cylinder 6 Air-Fuel Ratio Imbalance
Cylinder 6 fuel trim deviates significantly from the bank average — a single-cylinder injector or intake fault.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Common causes
Ordered by how often each turns out to be the cause.
- Injector clogged or leakingCommon
Parts involved
- Fuel Injector
P21A1 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.