P21F3Cylinder 12 Injector B Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P21F3 ends the B injector series of SAE J2012: a high signal on the cylinder 12 circuit, caused by a short to supply on the switched side. The series runs from P21CF to P21DA for opens and from P21DB to P21F3 for low/high pairs; the A injector equivalent here is P0295. Public manufacturer documents only reach cylinder 8 (GM's LT5 V8) or cylinder 4 (Mitsubishi), and no twelve-cylinder with dual injection could be documented, since Lamborghini's and Aston Martin's V12s use port injection alone. Should the code appear, the injector cannot open; cylinder 12 then relies on its other injector, and the driver stage takes the brunt of each switching attempt. GM's criteria for the same fault type serve as a guide: within 0.5 Ohm of power with the driver off. Low fault: P21F2.
- What you may notice
- Check engine light on
- Cylinder 12 lean or misfiring (P0312)
- Likely causes
- LikelyControl wire of the cylinder 12 B injector shorted to supply
- PossibleInjector coil with shorted windings
- RareDriver stage damaged by a lasting short
- 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: €150 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.