P21FAFuel Control System B Too Lean at 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
- P21FA is the bank 2 version of the idle lean check for the second fuel path. It applies to engines with two cylinder banks, a front oxygen sensor per bank and dual injection, such as Ford's 5.0 V8, which has combined port and direct injection since 2018. No manufacturer publishes this code; Ford monitors its port system per bank without separate idle cells and would store the fault as P2BF2. At idle the per-bank correction reacts strongly to small absolute errors, so a leak at bank 2's intake runners or gasket, or a partly blocked port injector on that side, are the first suspects while bank 1 stays clean. Drivers may notice an uneven idle or nothing beyond the warning lamp. The system A equivalent is P2189.
- What you may notice
- Check engine lamp on
- Uneven idle
- Likely causes
- PossibleIntake leak at bank 2 runners or gasket
- PossiblePartly blocked port injector on bank 2
- RareBank 2 front oxygen sensor reading 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 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.