Rear HO2S heater resistance inspection

WARNING: This page is about a different car, the 2004 Mazda 3. However, it is still accessible from the selected car via links, so may be relevant.

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

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