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The O2 sensor, when warmed up and running, should fluctuate back and forth between about 0.25 volts and 0.85 volts about 8 times in 10 seconds. (you may need to run the truck at about 2500 rpm to keep the sensor temperature high enough, but mine will fluctuate correctly at idle). If it is just sitting at 0.45 volts, most likely the sensor is dead.
To diagnose your O2 sensor you go to .... under the truck? No! You go to the diagnosis box attached to the fuse box. There is a connector labeled Ox1 which goes right to the sensor. You'll need a voltmeter with one of the lcd bars that imitates a needle (you're looking for up/down 8 times in 10 seconds; too fast to watch digits). Start it up, give it 30 seconds to warm up, then hold it at 2500 rpm (thereabouts). Look for up/down 0.25 to 0.85.
If it reads zero or 13.1 you've got a connection problem. If it sits at 0.45 I'd suspect a dead sensor. What about sitting at 0.25 or 0.85v? Then the O2 sensor is probably working, but you're running too rich (mileage problems) or too lean (knocking?). To track that down you need to lean out the mixture (create an air leak) or enrich it (propane?) That may be the "micky mouse" you're talking about.
Do you have a connector labelled Ox2? Welcome to California! That's the second O2 sensor downstream of the catalytic convertor. If that one switching back and forth at the same rate as your upstream sensor, your cat's dead.
Toyota recommends replacing the o2sensor at 80,000 miles. But you can buy 4 good voltmeters for the price of an O2 sensor. Do the test.
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