P21FBFuel Control System B Too Rich 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
- P21FB means bank 2's second fuel path is rich at idle while its correction already sits at the rich limit. The code requires an engine with a separate front sensor per bank and two injection paths; no maker documents it publicly. CARB section (e)(6.2.2) is the legal basis: once adaptive fuel control has used up the adjustment the manufacturer allows, a fault must be stored. Rich idle on one bank only typically comes from a port injector on that bank that leaks or sticks open, or from a bank 2 front sensor that reports too rich. If both banks show rich idle codes, look at shared items such as low-pressure regulation or fuel entering through crankcase ventilation. Fuel smell and a rough idle are possible; P2190 is the system A sibling.
- What you may notice
- Check engine lamp on
- Rough idle and fuel smell
- Likely causes
- PossiblePort injector on bank 2 leaking or sticking open
- PossibleBank 2 front oxygen sensor reading rich
- RareLow-pressure regulation too high or fuel from crankcase ventilation (if both banks rich)
- 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.