Circuit/System Description

This evaporative emissions (EVAP) system is a closed system. This vehicle's internal combustion engine (ICE), which is the consistent source of vacuum for conventional vehicles, only runs at predetermined times for regeneration. Therefore the need for a consistently reliable vacuum source - the EVAP system leak detection pump.

The EVAP leak detection pump assembly consists of three main components - a vacuum pump, a switching valve, and a pressure sensor. These DTC's deal only with the pump operation.

This pump is used for fuel tank pressure (FTP) sensor correlation or leak checking the EVAP system. The engine control module (ECM) has a wake-up timer, which is located in the hybrid powertrain control module 2. It activates the ECM at three calibratable times so that leak detection can occur.

The EVAP leak detection vacuum pump stuck on test is performed by comparing an initial EVAP leak detection pump pressure sensor, absolute, reading to a second reading after the EVAP leak detection pump switching valve transitions from vent to not venting, pump, position for a short period of time. The EVAP leak detection pump switching valve transitions back to vent position after the second EVAP leak detection pump pressure sensor reading. A difference between the two pressure readings indicates the EVAP leak detection vacuum pump is stuck on and sets DTC P145D.