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626 2.0L (Using Breakout Box)

  1. Warm engine to normal operating temperature. Turn ignition off. Connect 104-Pin Breakout Box (49 UN01 130) to PCM. Measure voltage at PCM terminal No. 60 for front sensor or No. 35 for rear sensor. See HO2S VOLTAGE (626 2.0L)  table.
  2. If voltage is not as specified, check wiring harness and connector between PCM and HO2S. Also check intake manifold system, fuel system and self-diagnostic system. Repair as necessary. If no problems are found, replace HO2S.
  3. To test HO2S heating element, allow sensor to cool to room temperature. Disconnect HO2S connector. Using ohmmeter, measure resistance between terminals "C" and "D" for 4-terminal sensor or "B" and "C" for 3-terminal sensor. See Fig 1 . Resistance should be about 6 ohms at 68°F (20°C). If resistance is not as specified, replace HO2S.
HO2S VOLTAGE (626 2.0L)

Application Volts
PCM Terminal No. 35 (Rear Sensor)
Acceleration 0-1.0
Deceleration 0-1.0
Idle 0-1.0
PCM Terminal No. 60 (Front Sensor)
Acceleration 0-1.0
Deceleration 0-0.5
Idle 0.5-1.0
Fig 1: Identifying HO2S Terminals (626 2.0L)
G98A10645Courtesy of MAZDA MOTORS CORP.