P21F6Fuel Control System B Too Lean Off Idle (Bank 2)
- 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
- P21F6 is the bank 2 form of P21F4 and only exists on V or flat engines whose cylinder banks each have their own front oxygen sensor and two injection paths. Here the part-load correction of the second path on bank 2 has reached its lean limit. No manufacturer documents this code publicly. Ford, whose 5.0 Coyote V8 gained direct injection on top of port injection for 2018, reports a lean port-injection fault on bank 2 as P2BF2 instead, without load zones, once long-term trim exceeds 25 % together with short-term trim above 1 % for 2 s. CARB demands a fault once adaptive control has used up its permitted range. If bank 1 stays clean, look at bank 2 alone: a clogged port injector or a wiring fault on that bank's injector harness.
- What you may notice
- Check engine lamp on
- Slight hesitation at part load
- Likely causes
- PossibleRestricted port injector on bank 2
- PossibleWiring or connector fault on the bank 2 injector harness
- RareLow pressure in the shared port fuel rail (if bank 1 also lean)
- 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: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.