G5: Check For O2 Sensor Failure

With the conditions held as in G4, 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 G7, G7: Check For O2 Sensor Continuity

No
Renew O2 sensor and reconnect plug(s).
GO to G6, G6: Stop