Middle/rear HO2S heater resistance inspection

WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Disconnect the middle/rear HO2S connector.
Measure the middle/rear HO2S resistance between terminals C and D.
- If not within the specification, replace the HO2S.
  Middle/rear HO2S heater resistance 2-50 ohms
  
  Fig 1: Identifying Middle/Rear HO2S Connector Terminals
  Courtesy of MAZDA MOTORS CORP.