P04FB: Crankcase ventilation pressure sensor reading does not make sense
Crankcase ventilation hose connection pressure sensor performance
Severity: Severity not verified — if the car runs badly, have it inspected
GM and Stellantis bulletins name this code and a repair but do not say whether the car is safe to drive with it set. Owners describe a steady check engine light, and one says remote start is blocked.
P04FB in short
P04FB means the engine computer thinks the crankcase ventilation pressure sensor is giving a signal that does not make sense. On GM 2.0L engines, GM says moisture can freeze inside that sensor in cold weather. Stellantis lists the same code on the 2015 ProMaster 3.0L. Have it checked soon if the light stays on.
Engines vent some combustion gas from the crankcase back into the intake. A pressure sensor in the ventilation hose lets the computer check that the hose is connected and the system is breathing normally. P04FB sets when that sensor does not behave as expected.
GM describes the code as the crankcase ventilation hose connection pressure sensor performance and says moisture or condensation can freeze in the sensor assembly in freezing weather on its 2.0L (RPO LSY) engines. Stellantis uses almost the same wording and fixes it with software on the 2015 ProMaster 3.0L.
Owners report the code coming back after a dealer clears it, and one dealer found moisture in the crankcase. GM calls its bulletin preliminary information, so the permanent fix may change.
Most likely causes
Cause 1: Condensation frozen in the crankcase pressure sensor (GM 2.0L, cold weather)
Supported by vehicle data- Why it ranks here
- GM TechLink and the PIP5841 bulletins name frozen moisture in the crankcase pressure sensor assembly as the cause of P04FB on its 2.0L LSY engine. A dealer in one owner complaint found moisture in the crankcase.
- What would change this
- Rises if the code set in freezing temperatures or after short cold trips and the sensor or hose holds moisture. Falls if no moisture is found and the sensor reading is steady.
Cause 2: Failed crankcase pressure sensor
Supported by vehicle data- Why it ranks here
- GM says to replace the sensor if the moisture condition returns after it was removed, so a repeat code points to the sensor. One owner reports the light returning after the dealer cleared the code.
- What would change this
- Rises if the code returns after the moisture was removed. Falls if the sensor works once dry.
Cause 3: Engine computer software (2015 ProMaster 3.0L)
Supported by vehicle data- Why it ranks here
- FCA bulletin 18-038-15 lists P04FB among codes addressed by a PCM update on the 2015 ProMaster 3.0L. The summary does not say P04FB alone is a software fault.
- What would change this
- Rises on a ProMaster 3.0L with the old software. Falls if the software is current.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read all stored codes and the freeze-frame, noting the outside temperature when P04FB set.
IfIt set in freezing weather on a GM 2.0L model
It meansFrozen moisture in the sensor is the first suspect.
IfIt is a 2015 ProMaster 3.0L
It meansAsk about the PCM update.
IfNeither applies
It meansInspect the sensor and hose.
Step 2: Have the PCV hose and crankcase pressure sensor removed and checked for frozen or standing moisture.
Warning:The sensor and hose sit near hot engine parts and the intake. Let the engine cool first, and leave the work to a shop.
IfMoisture or ice is present
It meansGM says to let it thaw, drain it, dry the sensor and hose, and clear the code.
Points to: Condensation frozen in the crankcase pressure sensor (GM 2.0L, cold weather)
IfThe sensor is dry and the code returns
It meansGM says to replace the sensor.
Symptoms
- Check engine light on, often in cold weather
- Light returns after the code is cleared
- Remote start does not work while the code is set (one owner report)
How to fix
Step 1: Ask a dealer whether the GM PIP5841 bulletin series applies to your 2.0L GM model.
Parts and cost context
- Crankcase ventilation (PCV) valve:GM replaces the crankcase pressure sensor only if moisture removal does not hold. Labor varies; get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
CadillacYour car
2019–2025 · 2.0L (RPO LSY)
Supported by vehicle dataGM PIP5841 bulletins cover P04FB on CT4, CT5, XT4, XT5 and XT6 (CT6 in 2019). Cause: condensation freezing in the crankcase pressure sensor.
PIP5841E (cadillac)Status unverified
Condensation freezing in the crankcase pressure sensor, P04FB
2019–2025ct4, ct5, ct6, xt4, xt5, xt6 · 2.0L (RPO LSY) · issued
GM preliminary information: moisture can freeze inside the crankcase pressure sensor and set P04FB. Only the NHTSA summary was read.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
ChevroletYour car
2020–2025 · Blazer · 2.0L (RPO LSY)
Supported by vehicle dataGM PIP5841 bulletins cover P04FB on the Blazer.
2025 · Equinox
Supported by vehicle dataOne 2025 Equinox owner says a dealer read P04FB and it returned after the code was cleared. No bulletin for the Equinox was found.
PIP5841E (chevrolet)Status unverified
Condensation freezing in the crankcase pressure sensor, P04FB
2020–2025blazer · 2.0L (RPO LSY) · issued
GM preliminary information: moisture can freeze inside the crankcase pressure sensor and set P04FB. Only the NHTSA summary was read.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
GMCYour car
2020–2024 · Acadia · 2.0L (RPO LSY)
Supported by vehicle dataGM PIP5841 bulletins cover P04FB on the Acadia. One owner says a dealer found moisture in the crankcase.
PIP5841E (gmc)Status unverified
Condensation freezing in the crankcase pressure sensor, P04FB
2020–2024acadia · 2.0L (RPO LSY) · issued
GM preliminary information: moisture can freeze inside the crankcase pressure sensor and set P04FB. Only the NHTSA summary was read.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
BuickYour car
2021–2025 · Envision · 2.0L (RPO LSY)
Supported by vehicle dataGM PIP5841 bulletins cover P04FB on the Envision.
PIP5841E (buick)Status unverified
Condensation freezing in the crankcase pressure sensor, P04FB
2021–2025envision · 2.0L (RPO LSY) · issued
GM preliminary information: moisture can freeze inside the crankcase pressure sensor and set P04FB. Only the NHTSA summary was read.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
P04FB questions
Why does P04FB come back after the dealer clears it?
If moisture keeps collecting in the sensor, the code can return. GM says to replace the sensor if it comes back after the moisture was removed.
Sources and review
- GM TechLink: Possible Condensation in Crankcase Pressure Sensor Assembly (PIP5841)
- FCA 18-038-15 Rev. B: 3.0L powertrain diagnostic and system enhancements (ProMaster)
- GM PIP5841A to PIP5841E: condensation freezing in the crankcase pressure sensor, DTC P04FB
- NHTSA complaint ODI 2175069: 2021 GMC, P04FB, moisture in the crankcase
- NHTSA complaint ODI 2108214: 2025 Chevrolet Equinox, P04FB crankcase ventilation pressure sensor issue
- NHTSA complaint ODI 2200181: 2025 Chevrolet, P04FB and remote start disabled
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error