Brake Vacuum Switch

To ensure the brake system is never compromised, a brake vacuum switch is installed on Auto stop/start vehicles to monitor vacuum reserves in the brake booster. The brake vacuum switch is mounted in the vacuum pipe and hardwired to the Engine Control Module (ECM). If the brake vacuum decreases below a set threshold while Auto stop/start is enabled, the ECM either:

• Restarts the engine to replenish the vacuum reserves.
• Inhibits the engine shutting down if vacuum reserves are not sufficient.

An example of vacuum reserves depleting, is by the driver repeatedly pressing the brake pedal while the engine is shutdown during an Auto stop/start. This action will initiate an engine restart when vacuum reserves decrease below the set threshold.

If a fault develops with the brake vacuum switch a Diagnostic Trouble Code (DTC) will be logged in the ECM.