P2C91Crankcase Ventilation System - Hose B Disconnected
- 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
- P2C91 is the second hose-specific PCV disconnection code: crankcase vapour line B is detected as open or broken, separately from line A (P2C90). Which physical hose carries the letter is the maker's choice; the code slot exists so that systems with two monitored lines can name the faulty one. The documented user is Stellantis on the Alfa Romeo Giulia and Stelvio (2021–22) with the 2.9-litre twin-turbo V6. Their two engine computers were reflashed in bulletins of 2023 and 2025 because P2C91 appeared together with crankcase pressure sensor B faults (P2C33) without a real leak. A hose that is genuinely loose lets oil mist or unmetered air escape, can upset idle and fuel trims, and keeps the lamp lit. Since 2025 every hose of this kind must be monitored, which is why such second codes appear.
- What you may notice
- Engine warning lamp
- Oil residue or hissing at a crankcase ventilation hose
- Possibly rough idle
- Likely causes
- LikelyEngine control software reporting a disconnection that is not there (Alfa Romeo 2.9 V6)
- PossiblePCV hose B loose, split or with a broken connector
- PossibleCrankcase pressure sensor B or its wiring faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €0 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.