P23F5 code meaning
Cylinder 4 Injector B Air-Fuel Ratio Imbalance
Powertrain system Generic code P23xx codes Check engine light
What P23F5 means
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.
P23F5 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of P23F5
- Check engine light on
- Slight vibration at idle
- Fuel trim shifted on the single bank
Common causes of P23F5
- Most likelyDeposits or wear in injector B of cylinder 4
- PossibleAir leak at the intake runner of cylinder 4
- Less likelyLow-pressure (port) fuel rail problem showing first at cylinder 4 (look for P2BF0/P2BF1)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injector b cyl 4
What each part of P23F5 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 3 | Area: ignition system or misfire. |
| F5 | The exact fault in that area. |
What to do next
- Note P23F5 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P23F5
What does P23F5 mean?
P23F5 means "Cylinder 4 Injector B Air-Fuel Ratio Imbalance". P23F5 concerns cylinder 4, the end cylinder of a four-cylinder engine. It is a generic code, so it means the same on every make.
Is it safe to drive with P23F5?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P23F5 fail an emissions test?
Yes, it can. P23F5 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P23F5 to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P23F5 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.