P24B9 code meaning
EVAP System Leak Detection Pump Pressure Sensor Circuit Range/Performance
Powertrain system Generic code P24xx codes Check engine light
What P24B9 means
P24B9 means the leak check module's pressure sensor delivers a signal that is electrically valid but not believable. GM's 2018 Volt table (ELCP) compares the absolute sensor reading with barometric pressure from the MAP sensor while pump and valve rest; a gap above 3,000 Pa at the engine-off wake-ups (roughly 4 to 11 h after shutdown) or above 15,000 to 20,000 Pa while driving counts as a fail, 50 of 63 samples, Type B. Mitsubishi's 2023 Outlander PHEV instead counts signal noise during the key-off test and fails after more than 20 fluctuations. FCA fixed P24B9 with PCM software on the 2017 Pacifica and the 2025 Grand Cherokee 4xe (18-079-25). P24BA and P24BB are the hard voltage limits.
P24B9 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P24B9
- Malfunction indicator lamp on
- EVAP leak test aborted, readiness not set
- Usually no noticeable change in driving
Common causes of P24B9
- Most likelyPressure sensor in the leak check module drifted or noisy
- PossibleEngine control software needing an update (FCA bulletins)
- PossibleMoisture or dirt in the module's pressure port
- Less likelyChafed wiring or loose pin causing signal disturbance
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EVAP leak detection pump pressure sensor
What each part of P24B9 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| B9 | The exact fault in that area. |
What to do next
- Note P24B9 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 P24B9
What does P24B9 mean?
P24B9 means "EVAP System Leak Detection Pump Pressure Sensor Circuit Range/Performance". P24B9 means the leak check module's pressure sensor delivers a signal that is electrically valid but not believable. It is a generic code, so it means the same on every make.
Is it safe to drive with P24B9?
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 P24B9 fail an emissions test?
Yes, it can. P24B9 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 P24B9 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P24B9 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.