Mazda RX-8 Workshop Manual page 1271

1. Disconnect the PCM connector.
2. Disconnect the A/F sensor connector.
3. Inspect the following wiring harnesses for an open or short circuit. (Continuity inspection)
Open circuit
If there is no continuity, there is an open circuit. Repair or replace the wiring harness.
A/F sensor terminal A and PCM terminal 2AD
A/F sensor terminal B and PCM terminal 2Z
Short circuit
If there is continuity, there is a short circuit. Repair or replace the wiring harness.
A/F sensor terminal A and body ground
A/F sensor terminal A and power supply
A/F sensor terminal B and body ground
A/F sensor terminal B and power supply