P21EFCylinder 10 Injector B Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P21EF stands for a high reading on the B injector circuit of cylinder 10. No public manufacturer document covers it, so the exact threshold is unknown; the closest documented model is GM's LT5 V8, where a switched-off low side within 0.5 Ohm of supply counts as a short and sets a Type A fault. A vehicle needs ten or more cylinders and two injectors each to use the code, which so far is documented only for Lamborghini's V10 in the Huracán. A short to power keeps the injector from ever opening, and switching against it strains the output stage, which may need replacement if the fault persisted. When P21EF shows up together with other high codes on the same bank, look for a common supply or connector. Low fault: P21EE; A injector high fault: P0289.
- What you may notice
- Check engine light on
- Cylinder 10 weak or misfiring under load
- Lean mixture on the second bank
- Likely causes
- LikelyCylinder 10 B injector control wire touching a live circuit
- PossibleShort inside a connector shared by several injectors
- PossibleInjector coil shorted
- RareOutput stage overloaded by the 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.