HO2S Heater Inspection

Disconnect the HO2S connector.
Measure the HO2S resistance between terminals C and D.
- If not as specified, replace the HO2S. (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION .)
HO2S heater resistance 2-50 ohms

Fig 1: Locating Heated Oxygen Sensor (HO2S)
Courtesy of MAZDA MOTORS CORP.