P21BFCold Start Cylinder 10 Injection Timing
- 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
- Cylinder 10 is the last cylinder of a V10 and exists otherwise only on twelve-cylinder engines. V10 engines are rare: Ford's 6.8-litre truck V10 (firing order 1-6-5-10-2-7-3-8-4-9, in the E-Series until 2019) and the 5.2-litre direct-injection V10 of Lamborghini and Audi. P21BF states that cylinder 10, during the cold-start heating phase, received its fuel at a different moment than targeted. No manufacturer documents the code publicly; the description rests on CARB's cold-start monitoring rules and on the system code P05EC, which GM checks across all cylinders of its diesels. If P021D (warm timing) or P0210 (injector circuit) are stored too, the cylinder 10 injector is the prime suspect; a cold-start pulse code does not exist for this cylinder.
- What you may notice
- Check engine light after one or more cold starts
- Uneven idle until the engine warms up
- Likely causes
- LikelyInjector of cylinder 10 aged or contaminated
- PossibleWiring or connector problem at injector 10
- RareEngine module software needing a cold-start calibration update
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €200 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.