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Oxygen Sensor

  1. Ensure engine is at operating temperature. Idle speed adjustment, voltage to O2 sensor heater and coolant temperature sensor must all be correct.
  2. Connect multimeter to differential pressure regulator using Adapter (1315A/1 ). See Figure . Start engine and idle for 2 minutes. Note control voltage at differential pressure regulator.
  3. Remove a manifold vacuum hose to induce a lean mixture. Control voltage must increase. If control voltage did not change, disconnect O2 sensor wire connector and ground harness end for 20 seconds. If control voltage changes, replace O2 sensor.
  4. If control voltage still does not change, perform wire harness checks for opens or shorts to ground or power. If harness checks okay, replace ECU.
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