Vacuum Switch: Testing and Inspection
Vacuum Switch Schematic:
To test the Vacuum Switch operation, proceed as follows.
SYSTEM OPERATION
1. Connect a voltmeter to the ECU harness connector terminal 5. DO NOT disconnect the connector. Use a thin piece of wire to backprobe the terminal.
2. Turn the ignition on and measure the supply voltage.
Voltage: 9 - 13 Volts.
3. With the engine warm and idling, measure the voltage at the ECU harness connector terminal 5.
Voltage: 0 - 0.6 Volts.
If the previous test fails to meet specifications, verify that the vacuum lines are connected and working before continuing. If vacuum is not present, refer to FUEL AND IGNITION for further Information.
COMPONENT TEST
Vacuum Switch Test:
1. Disconnect the green striped vacuum hose from the Device Box nipple.
2. Connect a hand operated vacuum pump to the nipple.
3. Disconnect the Vacuum Switch harness connector.
4. Connect a Ohmmeter to the Vacuum Switch harness connector terminals 2 and 4. and check for continuity.
Continuity: Should Not Exist.
5. Apply vacuum to the switch and measure when continuity exists.
Vacuum 26 KPa (7.5 in.Hg) Or less: No Continuity.
Vacuum 40 KPa (11.6 in.Hg) Or More: Continuity Exists.
If the test result is not as shown the switch should be replaced.
HARNESS TEST
1.Disconnect the Vacuum Switch harness connector and turn on the ignition.
2. Connect a voltmeter to the Vacuum Switch harness connector terminal 2. Measure the supply voltage.
Voltage: System Voltage.
3. Using an ohmmeter, check for continuity between the Vacuum Switch harness connector terminal 4 and ground.
Continuity: Should Exist.
If any of the previous tests produce unsatisfactory results, the harness will need to be repaired or replaced. Once repairs have been completed, road test the vehicle to confirm that the repair has corrected the problem.
If the same problem reoccurs, it is possible that there is an intermittent failure of the component or the ECU. Check for looseness at all harness junctions and test for an intermittent failure.