P24BB: EVAP System Leak Detection Pump Pressure Sensor Circuit High

P24BB is stored when the leak check module's pressure signal climbs above the top of its usable range. GM uses 4.85 V, about 97 % of the reference or roughly 120 kPa, again with 640 of 800 samples and Type B; the limit appears unchanged from the 2018 Volt up to GM's 2025 table 25OBDG03A for conventional ELCP systems. Mitsubishi's 2023 Outlander PHEV flags the code above 4.9 V lasting 2 s. Subaru lists P24BB with P24BA and P24B9 as faults to clear first when P2404 appears. A reading pinned high usually comes from an open ground, a signal wire touching a voltage source or an internal sensor fault, rarely from real pressure. P24BA covers the low side; P24B9 a signal that stays in range but disagrees with barometric pressure.

Low severity. Can I keep driving?Yes, you can normally keep driving. If there is a strong smell of gasoline, find the leak before continuing and do not smoke nearby.

Symptoms

Malfunction indicator lamp on
EVAP leak test not run, readiness incomplete

Most likely causes

Open sensor ground or signal wire, letting the input float high
Signal wire shorted to the 5 V reference or battery voltage
Pressure sensor inside the leak check module failed

What to check, in order

Start with the simplest. You can tick off each step.

Start with the fuel cap: tighten it fully and check its seal
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Inspect the hoses and connections around the tank and the charcoal canister
Use the scanner to test the purge and vent solenoid valves
Run a smoke test to find small leaks

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P24BB means

P: Powertrain: engine and transmission
2: Generic code: same on every make
4: Emissions
BB: Specific fault in that system

Frequently asked questions

Can I keep driving with code P24BB?

Yes, you can normally keep driving. If there is a strong smell of gasoline, find the leak before continuing and do not smoke nearby.

What causes code P24BB?

The most common causes are: open sensor ground or signal wire, letting the input float high; signal wire shorted to the 5 V reference or battery voltage; pressure sensor inside the leak check module failed.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.