Powertrain, generic (extended)

P24B8 EVAP System Leak Detection Pump Pressure Sensor Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P24B8 is the general circuit fault of the pressure sensor that sits inside an evaporative leak check module together with the pump and the switching valve. The sensor gets a 5 V reference from the engine computer and reports canister-side pressure during the engine-off leak test. No manufacturer documents P24B8 publicly; GM, Mitsubishi and Subaru use the more specific P24B9 to P24BB for this sensor. CARB requires such EVAP input components to be checked for circuit faults and implausible values. With this fault present, the leak test cannot be trusted and will not complete, so the EVAP readiness flag stays open. Typical findings are a broken reference or ground wire, a corroded module plug or a failed module.

Likely causes

Open or shorted 5 V reference, ground or signal wire to the leak check module
Corroded or loose connector at the leak check module near the canister
Pressure sensor inside the leak check module failed
Engine control module does not supply the sensor reference

Symptoms

  • Malfunction indicator lamp on
  • EVAP readiness monitor does not complete

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

P24B9P24BAP24BBP24BCP2400P2403

References: law.cornell.edu, gsi.ext.gm.com, mitsubishitechinfo.com.