Powertrain, generic (extended)

P24BB EVAP System Leak Detection Pump Pressure Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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.

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

Symptoms

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

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–450
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

evap leak detection pump pressure sensor

Related codes

P24BAP24B9P24B8P24BCP2404

References: gsi.ext.gm.com, mitsubishitechinfo.com, static.nhtsa.gov.