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Open Loop-3 Test

  1. Disconnect 6-wire connector at MCU and measure voltage at harness side terminal 5. Voltage should be 7±2 volts. If okay, continue to step 2)  . If not okay, repair harness wiring to coil.
  2. With engine at idle, test harness side terminal 9 for continuity to ground. There should be continuity. If okay, proceed to step  5. If not okay, continue to step 3)  .
  3. Disconnect vacuum hose leading to red switch and check for vacuum at idle. No vacuum should be present. If okay, continue to step 4)  . If not okay, correct vacuum hose routing or idle speed.
  4. Disconnect 4-wire connector at vacuum switch assembly and test switch side terminal 9 for continuity to ground. There should be continuity. If okay, repair open circuit in harness between MCU and vacuum switch assembly. If not okay, replace vacuum switch assembly and reconnect harness.
  5. Increase engine speed to 1500 RPM and recheck continuity. There should be no continuity. If okay, return engine to idle and replace MCU. If not okay, continue to step 6)  .
  6. With engine at 1500 RPM, measure vacuum to red switch. There should be 5 in. or more Hg vacuum. If okay, continue to step 7)  . If not okay, return engine to idle and repair routing or restriction of vacuum hose.
  7. Reconnect vacuum hose to red switch and disconnect 4-wire connector at vacuum switch assembly. With engine at 1500 RPM, test switch side terminal 9 for continuity to ground. There should be no continuity. If okay, repair shorted circuit in harness between MCU and vacuum switch assembly. If not okay, replace vacuum switch assembly and reconnect vacuum hoses and harness connectors.
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