Vacuum Switch Circuit
- Turn ignition OFF. Check vacuum hoses for cracks or leaks. Replace hoses as necessary. If no vacuum leaks are found, disconnect vacuum switch connector. For vehicles with 1-pin vacuum switch connector, go to next step. For vehicles with 2-pin vacuum switch connector, go to step 4).
- Check for continuity between terminal of vacuum switch and body ground. If continuity is not present, check vacuum switch installation or faulty ground connection. If okay, replace switch. If continuity is present, go to next step.
- Apply vacuum to switch with hand pump. No continuity should exist. If there is no continuity, go to step 5). If continuity exists, replace switch.
- Check for continuity between switch terminals. There should be continuity with no vacuum applied, and no continuity with vacuum applied. If switch operates as specified, go to next step. If switch does not operate as specified, replace switch.
- Reconnect vacuum switch connector. Disconnect vacuum pump connector. Check for continuity between connector terminal 2 and body ground. See Fig 1.
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
- If continuity is not present, check for open between terminal 2 and body ground. Also test body ground circuit. If continuity is present, check vacuum pump operation.
- Connect vacuum gage to vacuum pump port farthest from pump motor. Connect jumper wire from battery positive to pump motor terminal 1, and from negative battery terminal to pump motor terminal 2. Pump motor should operate. If at least 7.87 In. Hg. (26.7 kPa) is present, pump is okay. Go to next step. If pump does not operate as specified, replace pump.
- Reconnect vacuum switch and pump connectors. Disconnect computer connector and check for continuity between terminal 9 and body ground. See Figure.
- If no continuity is present, check for open between terminal 9 of computer and terminal of vacuum switch. If continuity is present, start engine and let engine idle.
- Check for continuity between terminal 9 and body ground. If continuity is present, check for short circuit between terminal 9 of computer and terminal of vacuum switch.
- If no continuity is present, stop engine and check for continuity between vacuum pump terminal (Blue/Red wire) and body ground. If no continuity is present, check for open in Blue/Red wire between terminal 1 of computer and terminal of vacuum pump. See WIRING DIAGRAMS .
- If continuity is present, check for continuity between vacuum pump terminal (Blue/Red wire) and body ground with vacuum pump connector disconnected. If continuity is present, check for short in Blue/Red wire between terminal 1 of computer and terminal of vacuum pump. If no continuity is present, replace cruise control computer.