Mazda RX-8 Workshop Manual page 1272

A/F Sensor Heater Resistance Inspection
1. Disconnect the A/F sensor connector.
2. Measure the resistance between A/F sensor terminals C and D.
If not within the specification, replace the A/F sensor. (See
(A/F) SENSOR REMOVAL/INSTALLATION
A/F sensor heater resistance
1—10 ohms
A/F Sensor Heater Circuit Open/short Inspection
AIR FUEL RATIO
[13B-MSP].)