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Code 45, Oxygen Sensor Circuit Rich Exhaust Indicated

The ECM supplies a voltage of approximately .45 volt between ECM terminals No. 3 and 20 (if measurement is taken with a 10-megohm DVOM, reading may be as low as .32 volt). O2 sensor varies the voltage within a range of about one volt if exhaust is rich and down to about .10 volt if exhaust is lean. When sensor temperature is less than 600°F (316°C), the sensor acts like an open circuit and will not produce voltage. An open sensor circuit will cause an "Open Loop"" condition

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Code 45 will set when O2 sensor signal voltage on circuit No. 412 remains less than .6 volt for 2 minutes or more, system operating in "Closed Loop", O2 sensor has reached a temperature of 158°F (70°C) and engine is running for 5 minutes or more at part throttle
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