D3 - Component Isolation Check

- Key OFF.

Vacuum Gauge:

- Connect the vacuum gauge to the same point as in step D1, but leave the rest of the system connected.

- Push down on brake pedal.

- Key ON, engine running.

- Does the brake pedal move downward when the engine is started?

YES -- Go to D4.

NO -- Disconnect each component one at a time and repeat the test procedures in step D3 until the leaking component is found. Plug the disconnected vacuum booster hose while performing the test procedures. Repair or replace as required.