P21D2Cylinder 4 Injector B Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P21D2 reports an open in the drive circuit of the B injector on cylinder 4. On four-cylinder engines with dual injection it is the last of the set, for example Ford's 2.0 EcoBoost from 2022 or the 2.3 introduced for the 2024 Mustang, both of which added port injectors to direct injection. Ford tests it like its siblings, continuously with at least 11 V and a 5 s window, and assigns letter A to the direct injector (P0204). Mitsubishi, whose Eclipse Cross uses B for the direct injectors, has no open code here and files such faults under the low code P21E2. On Ford's 3.5 V6 cylinder 4 opens the second bank. In GM's 2019 LT5 module the check samples every 100 ms. Expect a misfire on cylinder 4.
- What you may notice
- Check engine light on
- Misfire on cylinder 4 (P0304)
- Uneven idle
- Likely causes
- LikelyOpen winding in the cylinder 4 port injector
- PossibleWire broken at a bend or clip near the intake manifold
- PossibleCorroded or loose injector connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €80 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.