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HO2S Inspection

  1. Warm up the engine to normal operating temperature.
  2. Access the following PIDs using the M-MDS: (See ON-BOARD DIAGNOSTIC TEST .)
    • VSS (Vehicle speed)
    • RPM (Engine speed)
    • O2S12 (HO2S voltage)
  3. Drive the vehicle and decelerate the engine speed by releasing the accelerator pedal fully when the engine speed is 3, 000 RPM or more.
  4. Verify that the HO2S voltage (PID: O2S12) of 0.6 V or more,  one time or more, then verify that the HO2S voltage (PID: O2S12) is 0.3 V or less  while decelerating as shown in the illustration.
Fig 1: Heated Oxygen Sensor Voltage Graph
G07620734Courtesy of MAZDA MOTORS CORP.