P21F7Fuel Control System B Too Rich 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
- P21F7 sets when the second fuel path on bank 2 has to remove more fuel above idle than its rich limit permits. It needs an engine with two banks, separate front sensors and dual injection; inline engines such as Audi's 2.5 TFSI only have the bank 1 codes. No manufacturer publishes criteria for P21F7. An FCA patent for port plus direct injection engines explains the idea behind such split codes: a fault seen while only one path is fuelling is assigned to that path, whereas a fault during mixed operation goes to a general code such as P0175. When only this bank is affected, a leaking port injector on bank 2 or a bank 2 front sensor that reads rich is plausible; if both banks are rich, check what they share, such as pressure regulation. P2180 is the system A counterpart.
- What you may notice
- Check engine lamp on
- Increased fuel consumption
- Likely causes
- PossibleLeaking port injector on bank 2
- PossibleBank 2 front oxygen sensor reading rich
- RareLow-pressure regulation too high (if bank 1 also 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 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.