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Oxygen Sensor Monitor

  1. 1)  To check if the front oxygen sensor is switching between rich and lean, switch to mode 2 (diagnostic mode). See RETRIEVING CODES . Start engine while in mode 2 and run until fully warm. Run engine at 2000 RPM without load for 2 minutes, while monitoring MIL.
  2. 2)  If MIL flashes at least 5 times every 10 seconds, this indicates front oxygen sensor is functioning and fuel mixture is switching between lean and rich. This is an indication fuel mixture control system is okay.
  3. 3)  If MIL stays lit all or most of the time, a lean condition is indicated. Mixture control may be in open loop, ensure engine is fully warm. Fuel mixture may be lean or oxygen sensor may be faulty. Check for DTCs and repair if necessary. Check for conditions that could cause lean mixture, if okay, replace oxygen sensor.
  4. 4)  If MIL is off all or most of the time, a rich condition is indicated. Check for DTCs and repair as necessary. Check for conditions that could cause a rich condition, if okay, replace oxygen sensor.
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