P2C91 code meaning
Crankcase Ventilation System - Hose B Disconnected
Powertrain system Generic code P2Cxx codes Check engine light
What P2C91 means
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.
P2C91 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.2 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P2C91
- Engine warning lamp
- Oil residue or hissing at a crankcase ventilation hose
- Possibly rough idle
Common causes of P2C91
- Most 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
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Crankcase vent hose bCrankcase pressure sensorIntake manifold
What each part of P2C91 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| C | Area: hybrid propulsion. |
| 91 | The exact fault in that area. |
What to do next
- Note P2C91 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2C91
What does P2C91 mean?
P2C91 means "Crankcase Ventilation System - Hose B Disconnected". P2C91 is the second hose-specific PCV disconnection code: crankcase vapour line B is detected as open or broken, separately from line A (P2C90). It is a generic code, so it means the same on every make.
Is it safe to drive with P2C91?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2C91 fail an emissions test?
Yes, it can. P2C91 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2C91 to fix?
Difficulty: easy. A typical repair takes 0.2 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P2C91 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.