Circuit/System Description
WARNING: This page is about a different car, the 2019 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
The evaporative emission (EVAP) system uses a EVAP leak detection pump to test for system leaks. The EVAP leak detection pump assembly consists of three main components:
- EVAP leak detection pump with reference orifice
- EVAP leak detection pump switching valve
- EVAP leak detection pump pressure sensor
The EVAP leak detection pump pressure sensor performs a correlation to barometric pressure (BARO). After a short delay period, the EVAP leak detection pump pressure sensor, absolute, reading is compared to the BARO. Large deviations will increment the fail counter threshold and sets a P24B9.
There are two different threshold calibrations used in the comparison to the BARO. A smaller threshold is used when there has been a recent BARO update and then a larger threshold value is used when there has not been a recent BARO update.