Here are the results from voltage test.

Voltmeter +-lead connected to lead from O2-sensor, -lead on bumper.
Engine not run for three hours and  O2-sensor not connected to lead to
ECU

0 volts from 0 to 120 seconds

0.13 volts at 150 seconds

0.53 volts at 180 seconds

0.30 volts at 210 seconds

engine stalls out at 240 seconds

connected O2-sensor to lead to ECU

restarted engine

0.45 to 0.55 volts

0.6 to 0.8 volts after engine at temperature and engine at about 2000
rpm

0.4 to 0.7 volts with rapid change within that range with engine at idle

Any thoughts on good or bad?

John