P04FB on 2020-2025 Cadillac CT4 — Crankcase Ventilation Hose Connection Pressure Sensor Performance
1 vehicles · 1 makes
Most Reported On
P04FB is an OBD-II diagnostic trouble code meaning “Crankcase Ventilation Hose Connection Pressure Sensor Performance.” The crankcase ventilation pressure sensor is a transducer that outputs a voltage proportional to the gauge pressure between the crankcase ventilation hose and atmosphere; the ECM uses it to monitor PCV system integrity, watching the pressure pulses that track engine airflow and piston motion. P04FB sets when the ECM sees the sensor signal fail to behave as expected — GM's published criterion is the reported pressure remaining outside roughly −0.62 to 0.62 kPa (−0.09 to 0.09 psi) for more than about one second under conditions where a change should be present. In other words the sensor reads a plausible but unchanging or implausible value, so the PCV monitor cannot run. This code is most commonly reported on 2020-2025 Cadillac CT4.
Common Causes
Diagnostic Tools
This is a powertrain code, so a basic OBD-II reader can read it. These read P04FB.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple code reader for engine (P) codes on many compatible OBD-II vehicles. It does not support every vehicle or hybrid/EV application, and it does NOT read body, chassis or network codes; confirm exact-vehicle compatibility before buying.
- Read & clear engine (P) codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth scanner with a companion app that reads beyond the engine module — ABS, SRS and transmission — plus manufacturer-specific codes on many vehicles.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X V3.0 Elite OBD-II Scanner
by LAUNCH
Handheld scanner covering the four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level tablet with all-system coverage and bi-directional control, so you can command a module rather than only read it.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
What you can do yourself, and what needs a shop
Reading the code, clearing it, and watching whether it returns is a driveway job with the right scanner. These steps are not:
- Module programming or software updates — needs the manufacturer software or a J2534 pass-through with a paid subscription.
- Replacing a control module — most are VIN-programmed and immobilizer-registered, so a new one does nothing until it is coded to your car.
- Airbag/SRS component work — a stored fault can deploy a live device.
If the vehicle is still under warranty, check for an open recall or technical service bulletin before buying anything — the repair may already be covered.
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
FAQ
What does P04FB mean?
P04FB stands for "Crankcase Ventilation Hose Connection Pressure Sensor Performance." The crankcase ventilation pressure sensor is a transducer that outputs a voltage proportional to the gauge pressure between the crankcase ventilation hose and atmosphere; the ECM uses it to monitor PCV system integrity, watching the pressure pulses that track engine airflow and piston motion. P04FB sets when the ECM sees the sensor signal fail to behave as expected — GM's published criterion is the reported pressure remaining outside roughly −0.62 to 0.62 kPa (−0.09 to 0.09 psi) for more than about one second under conditions where a change should be present. In other words the sensor reads a plausible but unchanging or implausible value, so the PCV monitor cannot run.
What are the most common causes of P04FB?
The most common causes of P04FB are: Ice, water or fuel condensate forming in the crankcase ventilation hose or in the sensor port during cold or short-trip operation, blocking the pressure signal, Failed crankcase ventilation pressure sensor, Disconnected, split, collapsed or oil-fouled crankcase ventilation hose, Restricted or blocked PCV passage / oil separator, Open, shorted or corroded sensor wiring or connector. The specific cause varies by vehicle.
How much does it cost to fix P04FB?
Repair costs vary widely depending on the root cause and vehicle.
Which vehicles are affected by P04FB?
Au7o has documented P04FB across 1 vehicle models from 1 manufacturers: Cadillac.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.