Theory Of Operation

GENERAL OPERATION:  The Electric Vacuum Pump (EVP) system is designed to provide supplemental vacuum during low engine vacuum conditions. The EVP is activated when the vacuum in the Brake Vacuum Booster reaches a minimum calibrated threshold. The EVP is especially important on vehicle applications where the engine is not running the entire time, such as for hybrid or Stop/Start equipped vehicles. This system maintains a consistent brake pedal feel under all driving conditions. The Vacuum Pump is connected to the engine and the Brake Booster through a series of hoses and one-way flow check valves. A Vacuum Pressure Sensor mounted in the Brake Vacuum Booster is hard-wired to the Anti-Lock Brake (ABS)/Electronic Stability Program (ESP) Module. The Vacuum Pressure Sensor signal information is then sent to the Powertrain Control Module (PCM) over the CAN Bus. The PCM energizes the Vacuum Pump Relay through a Low Side Driver (LSD)  to provide Battery voltage to the vacuum pump and control operation.