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Oxygen Sensor

  1. Start engine and warm to operating temperature. Pull back connector seal at oxygen sensor. Using a digital voltmeter with at least a 10-megohm input impedance, backprobe oxygen sensor connector.
  2. With engine at idle, remove a large vacuum hose from intake manifold to create a large vacuum leak (without causing engine to stall). Voltage reading at oxygen sensor should drop. Reconnect vacuum line and voltage should increase. If voltage readings do not respond as specified, replace oxygen sensor.
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