For 1990-2009 cars

1. Remove the engine vacuum hose from the vacuum brake booster.
2. Install a vacuum gage to the engine vacuum hose.
3. Start the engine. Verify the transmission is in Park or Neutral.
4. Allow the engine to idle until the engine reaches normal operating temperatures.
5. Check to see if the engine vacuum meets or exceeds the minimum specification.

Specification
The minimum engine vacuum is 17 in Hg (57.6 kPa)

6. Turn the ignition OFF.
7. If the engine vacuum reading meets or exceeds the minimum specification, verify the check valve operates properly.
8. If the engine vacuum reading is less than the minimum specification, inspect the vacuum booster pipe and hoses for the following conditions.

• | Loose connection to the engine

• | Collapse, deformation or contamination

• | Cracks, cuts, dry-rot

9. Replace any defective vacuum booster pipe or hose. Refer to Vacuum Brake Booster Hose Replacement .

Important: If the engine does not produce proper vacuum, the vehicle will have driveablilty conditions in addition to the brake assist condition.

10. If none of these conditions exist on the pipe and hoses, then there is an engine vacuum source problem. Check the engine vacuum system. Refer to the following:

• | Diagnostic Starting Point - Engine Controls in Engine Controls -- 1.6L

• | Diagnostic Starting Point - Engine Controls in Engine Controls -- 2.0L

• | Diagnostic Starting Point - Engine Controls in Engine Controls -- 2.5L