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626 2.0L (Using Breakout Box)

  1. Warm engine to normal operating temperature. Turn ignition switch off. Connect 104-Pin Breakout Box (49-UN01-130) between PCM and PCM harness connector. See Figure .
  2. Voltage Inspection

    Turn ignition switch on. Measure voltage at PCM terminal No. 60 (front HO2S) or No. 35 (rear HO2S). See HO2S VOLTAGE (626 2.0L)  table. If voltage is not as specified, check wiring harness and connectors between PCM and HO2S. See WIRING DIAGRAMS article. Also check intake-air system, fuel system and self-diagnostic system. Repair as necessary. If system or wiring harness problems are not present, replace HO2S.
  3. HO2S Heater Resistance Inspection

    Disconnect HO2S 4-pin connector. Using ohmmeter, measure resistance between HO2S 4-pin connector terminals "C" and "D". See Fig 1 . Resistance should be about 6 ohms. If resistance is not as specified, replace HO2S.
HO2S VOLTAGE (626 2.0L)

Application Volts
Rear HO2S
Acceleration About 0
Deceleration About 0
Idle About 0
Front HO2S
Ignition On Less Than 1.0
Acceleration 0.5-1.0
Deceleration 0-0.5
Idle
After Warm Up 0.1-0.9
Engine Cold Less Than 0.5
Fig 1: Identifying HO2S Terminals (626 2.0L)
G00032308Courtesy of MAZDA MOTORS CORP.