P00F4 code meaning
Humidity Sensor Circuit Low
Powertrain system Generic code P00xx codes Check engine light
What P00F4 means
The humidity sensor measures the relative humidity of the intake air; on documented vehicles it is built into the mass air flow sensor or a combined sensor. The engine control module uses the value, for example, to correct torque and in emission models. One documented design is capacitive and reports humidity as a pulsed signal with a duty cycle that the control module converts back. P00F4 means the signal is below its valid range (for example a duty cycle near zero), typically because the signal wire is shorted to ground or the sensor supply is missing.
P00F4 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1 hours
- Clears after repairAfter a drive cycle
Symptoms of P00F4
- Check engine light on
- Usually no noticeable symptoms
- Slightly uneven torque or higher consumption possible
Common causes of P00F4
- Most likelySignal wire shorted to ground
- PossibleSensor or combined air flow sensor faulty
- PossibleSensor supply missing
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Humidity sensorMass air flow sensorHumidity sensor wiring
What each part of P00F4 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| F4 | The exact fault in that area. |
What to do next
- Note P00F4 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 P00F4
What does P00F4 mean?
P00F4 means "Humidity Sensor Circuit Low". The humidity sensor measures the relative humidity of the intake air; on documented vehicles it is built into the mass air flow sensor or a combined sensor. It is a generic code, so it means the same on every make.
Is it safe to drive with P00F4?
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 P00F4 fail an emissions test?
Yes, it can. P00F4 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 P00F4 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P00F4 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.