H6: Check For O2 Sensor Failure

With the conditions held as in H5, run the engine at 1500 rpm for approximately 3 minutes.

Does the displayed voltage drop below 400mV and rise above 500mV, cycling approximately every 180 seconds?

Yes
GO to H8, H8: Check For O2 Sensor Continuity

No
Renew O2 sensor. Reconnect plug(s)
GO to H7, H7: Stop