P23F5Cylinder 4 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
- P23F5 concerns cylinder 4, the end cylinder of a four-cylinder engine. Many four-cylinder units now carry two injectors per cylinder: Toyota's 8AR-FTS turbo (D-4ST) and its Dynamic Force engines such as the M20A (D-4S), Hyundai's Smartstream G2.5 GDi and T-GDi, and the updated Ford 2.3 EcoBoost of the 2024 Mustang. With a single bank, all cylinders share one wide-band sensor ahead of the catalyst; GM, for example, rates imbalance from how strongly that signal varies from one firing event to the next. No manufacturer links P23F5 to a vehicle in public papers. If P2BF0 or P2BF1 (Fuel Control System B lean or rich) appear as well, the whole port-fuel path is off rather than one injector. P219F and P21D2 cover the same cylinder.
- What you may notice
- Check engine light on
- Slight vibration at idle
- Fuel trim shifted on the single bank
- Likely causes
- LikelyDeposits or wear in injector B of cylinder 4
- PossibleAir leak at the intake runner of cylinder 4
- RareLow-pressure (port) fuel rail problem showing first at cylinder 4 (look for P2BF0/P2BF1)
- 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: €80 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.