Mazda CX-9 Grand Touring 2009 Manual page 851

If there is continuity, the circuit is shorted. Repair or replace the harness.
HO2S (RH) terminal A and power supply
HO2S (RH) terminal A and body ground
HO2S (RH) terminal B and power supply
HO2S (RH) terminal B and body ground
HO2S (RH) terminal C and body ground
HO2S (RH) terminal D and power supply
HO2S (LH) terminal A and power supply
HO2S (LH) terminal A and body ground
HO2S (LH) terminal B and power supply
HO2S (LH) terminal B and body ground
HO2S (LH) terminal C and body ground
HO2S (LH) terminal D and power supply
REAR HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [MZI-
3.7]
HO2S (LH) REMOVAL/INSTALLATION
1. Disconnect the negative battery cable.
2. Disconnect the HO2S (LH) connector.
NOTE:
3. Remove the HO2S (LH) using the SST.
NOTE:
4. Install in the reverse order of removal.
2008 Mazda CX-9 Grand Touring
2008 ENGINE Control System (MZI-3.7) - Mazda CX-9
If necessary, lubricate the HO2S (LH) with Penetrating and Lock
Lubricant loosen to aid in removal.
Apply a light coat of anti-seize lubricant to the threads of the HO2S.