Both Sensors

NOTE:

Disconnect the HO2S electrical connector.

Fig 1: Disconnecting HO2S Electrical Connector
Courtesy of MAZDA MOTORS CORP.
Remove the heated oxygen sensors (HO2S) from the exhaust manifolds.
- If necessary, lubricate the heated oxygen sensors to assist in removal.
  
  Fig 2: Removing Heated Oxygen Sensors (HO2S) From Exhaust Manifolds
  Courtesy of MAZDA MOTORS CORP.
Disconnect the HO2S electrical connector.

Fig 3: Disconnecting HO2S Electrical Connector
Courtesy of MAZDA MOTORS CORP.
Remove the heated oxygen sensors from the exhaust pipe using the Oxygen Sensor Wrench.
- If necessary, lubricate the heated oxygen sensors to assist in removal.
  
  Fig 4: Removing Heated Oxygen Sensors From Exhaust Pipe
  Courtesy of MAZDA MOTORS CORP.
  NOTE:
  - Apply a light coat of anti-seize compound to the threads of the heated oxygen sensors.
Install in reverse order of removal.
Tightening torque:

{ 36-46 N.m, 27-33 ft.lbf }

Fig 5: Connecting HO2S Electrical Connector
Courtesy of MAZDA MOTORS CORP.

Fig 6: Installing Heated Oxygen Sensors - With Torque Specification
Courtesy of MAZDA MOTORS CORP.