Powertrain, generic (extended)

P2C91 Crankcase Ventilation System - Hose B Disconnected

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Engine control software reporting a disconnection that is not there (Alfa Romeo 2.9 V6)
PCV hose B loose, split or with a broken connector
Crankcase pressure sensor B or its wiring faulty

Symptoms

  • Engine warning lamp
  • Oil residue or hissing at a crankcase ventilation hose
  • Possibly rough idle

Repair estimate

DifficultyEasyDIY possible
Parts and labour€0–300
Time0.2–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

crankcase vent hose bcrankcase pressure sensorintake manifold

Related codes

P2C90P04DBP04FCP2C33P2C32

References: static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.