626 2.0L (Using New Generation Star (NGS) Scan Tool)

WARNING: This page is about a different car, the 2001 Mazda Protege, 2001 Mazda Millenia, 2001 Mazda MX-5 Miata, 2001 Mazda MPV, and 2001 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

Warm engine to normal operating temperature. Connect NGS scan tool to DLC-2. DLC-2 is located under left side of instrument panel, right of steering column. Using scan tool, access DIAGNOSTIC DATA LINK menu, and select PCM. Highlight and select PID/DATA MONITOR AND RECORD.
Turn ignition on. Select O2S11 PID for front HO2S or O2S12 PID for rear HO2S. See PIN VOLTAGE/PID VALUE CHARTS article. If voltage is not as specified, check wiring harness between PCM and HO2S. Also check intake manifold system, fuel system and self-diagnostic system. Repair as necessary. If no problems are present, replace HO2S.
To test HO2S heating element, allow sensor to cool to room temperature. Disconnect HO2S connector. Using ohmmeter, measure resistance between appropriate HO2S 4-pin connector terminals "C" and "D". See Figure . Resistance should be about 6 ohms at 68°F (20° C). If resistance is not as specified, replace suspect HO2S.