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O2 Sensor

  1. Before starting to test O2 sensor, check following conditions: engine oil temperature at 176°F (80°C) minimum, radiator fan must cycle at least once, pressure gauges NOT connected, exhaust system free of leaks, O2 sensor control working properly, all electrical units turned off (radiator fan and A/C must be off during test), and engine run to 3000 RPM for 2 minutes several times if any fuel line has been recently disconnected.
  2. Connect test harness between differential pressure regulator and vehicle harness. Connect multimeter to test harness. Run engine at idle. After 2 minutes running time, O2 sensor is heated up enough to work.
  3. Current reading should fluctuate at idle. If not, check current reading at 3000 RPM. If reading fluctuates now, O2 sensor is good. If reading does not fluctuate at 3000 RPM, replace O2 sensor.
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