P23F9Cylinder 8 Injector B Air-Fuel Ratio Imbalance
- 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
- P23F9 points to cylinder 8, the highest number on any V8. GM's 2019 tables for the LT5 Corvette show how far a V8 with port and direct injection resolves imbalance in practice: only bank by bank. For bank 2 the monitor samples the front oxygen sensor once per cylinder event, normalises the variance against a map and fails when the filtered ratio exceeds 0.75, a Type A fault that turns on the MIL after one trip. A cylinder code that also names the injector therefore needs more than the bank-level method can deliver, and no manufacturer has published that it uses P23F9. Ford's Coyote 5.0 since 2018 and Toyota's 2UR-GSE are further V8s with dual injectors. Which bank cylinder 8 sits on follows the maker's numbering; P21A3, P0308 and P21D6 help.
- What you may notice
- Check engine light on
- Bank-level imbalance code (P219A/P219B) stored as well
- Normal drivability in most cases
- Likely causes
- LikelyInjector B of cylinder 8 with wrong flow rate
- PossibleLeak at the intake runner or PCV connection near cylinder 8
- RareFront oxygen sensor of the bank giving a distorted signal
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €120 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.