Brake Booster Vacuum Sensor
WARNING: This page is about a different car, the 2018 Lincoln MKC. However, it is still accessible from the selected car via links, so may be relevant.
The brake booster vacuum sensor is a piezoelectric device used by the ABS module to monitor the vacuum in the brake booster. The sensor is hardwired to the ABS module by 3 circuits. One circuit is for the 5 volt sensor supply, one circuit is for sensor ground and one circuit is for sensor output. The sensor output is a serial data stream which communicates the vacuum level in the booster to the ABS module.
The ABS module sends the vacuum level information to the PCM for correct automatic start-stop system operation.