System Operation
WARNING: This page is about a different car, the 2019 Buick Cascada, 2018 Buick Cascada, and 2017 Buick Cascada. However, it is still accessible from the selected car via links, so may be relevant.
The pump can be switched on and off by the Electronic Brake Control Module based on the required vacuum. Pressure variations during braking can be measured, and the pump can be activated to generate additional vacuum if required to increase the braking force.
The pump runs for the first 5 seconds after engine running to perform a self test. Engine running, the pump may run another 30 seconds and then turns off, due to the timer relay. The pump has a maximum run time of 180 seconds per ignition cycle with engine running, when it reaches the maximum run time the pump shuts down to cool off and will not allow the pump to run again until the next engine run cycle.