Checking Pressure Sensor

Turn the ignition switch to the OFF position. Evacuate the vacuum system by depressing the brake pedal five times. Do not touch the brake pedal and turn the ignition switch to the ON position. If vacuum pump stops after approx. 10 seconds, do not touch the brake pedal. If vacuum pump does NOT start within one minute, check vacuum system for leaks.

If vacuum pump does not stop after approx. 10 seconds, check power supply to vacuum pressure switch. Move the wiring harness at several spots and in several directions to reveal intermittent breaks and short-circuits. Check switches, connectors and crimp connections for oxidation, retracted pins and pin clamping force. Repair as necessary. If okay, check power and ground at vacuum pump unit.