Brake Vacuum Assist (3.0L Petrol Vehicles Only)

Operation of Brake Vacuum Assist generally occurs at the beginning of an ignition cycle when brake booster vacuum levels are low; refer to Brake Booster Vacuum sensor, below.

Brake vacuum assist operation will be recognized by the driver experiencing a vibrating brake pedal and slight modulator noise. This will be similar to that experienced when ABS system is operating.

As the engine warms up, Brake Vacuum Assist operation will become less frequent. However, it can be become more active when vacuum levels are low due to driving at high-altitudes, or during frequent heavy-braking.

Noise levels during Brake Vacuum Assist may vary with initial system activity being the loudest observed. In some circumstances initial activity may be interpreted as a 'thump' noise, particularly if there is no immediate and significant Brake Vacuum Assist functionality.

In this circumstance system behavior is normal and should not be a cause for fault investigation.