Induce a lean condition, remove a vacuum hose...O2 will go low at.1 volts. Now go rich by adding fuel...with propane bottle at intake...does the O2 sensor show high at.9 volts? If so it's seeing the mixture. That's all it does. It reports back to the comp....and the comp make adjustments. It's just a messanger, it goes high and low according to the comp output. If the ECS does not respond then you have other issues. Remember, Low voltage on any O2 is LEAN. High voltage is RICH