Vacuum Pump, Brake System

To improve the strength of the vacuum for the brake servo, a vacuum pump was introduced on certain car models during the latter part of the model year. When engine vacuum is insufficient, pressure switch 458 closes and the coil in relay 460 is supplied with current. The relay operates and motor 459 starts. The vacuum pump runs until the correct level of vacuum is attained, causing the pressure switch to open and the pump to stop.

Grounding of the relay was changed in the interests of better DRIVEABILITY. It is now controlled via the Trionic control module.