Electric Vacuum Pump
WARNING: This page is about a different car, the 2010 Mercury Milan, 2010 Lincoln MKZ, and 2010 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
When the combustion engine is not running, an electric vacuum pump is used to maintain vacuum inside the brake booster. The ABS module turns the electric vacuum pump on and off through the use of a mechanical relay and a solid state relay. If the ABS module detects a vacuum pump motor circuit concern, a vacuum system leak or a vacuum pump performance concern, a DTC will set in the ABS module and the combustion engine will run to provide vacuum for the brake booster.