P04FBCrankcase Ventilation Hose Connection Sensor Range/Performance
- 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
- The crankcase ventilation hose connection sensor is a pressure sensor in the PCV line that measures pressure relative to atmosphere; it is the basis for detecting a disconnected hose (P04DB). P04FB is its plausibility check: GM's 2.0-litre LSY checks the zero point with the engine stopped (at least 10 s, coolant 70 °C or more) – a reading outside ±0.63 kPa or a frozen value sets the code in 128 of 160 samples, MIL after two trips. The disconnection check P04DB is then not possible.
- What you may notice
- Check engine light on
- No change in driving
- Likely causes
- LikelyPressure sensor drifting (zero point error)
- PossibleSensor port or line blocked by oil or ice (value frozen)
- PossibleContact resistance in supply, ground or signal
- RareResidual crankcase pressure after switch-off (blocked ventilation)
- 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: €50 – €220
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.