OBD2 doesn't see oxygen sensor

The only proper way to check the O2 sensor (and the air/fuel mixture sensor if equipped with both) is to use an OBDII interface device. What you did is NOT the correct method and therefor, your findings invalid.

OK.... BUT WHY I DIDN'T GET CHECK ENGINE LIGHT ON??? THIS IS MY MAIN QUESTION.... THANKS ANDREW

Your original problem: I own Toyota Echo 2000 (100k) Recently it started to vibrate more then usualy. I replacet all spark plugs, tested all sensors. Everything seems to be ok. I suspect oxygen sensor. I think mix is too lean and sensor can't sense it.

Your looking in the wrong place, forget the O2 sensor. When is it vibrating? At idle, full throttle or driving down the road? Is it driveable? Have you looked at Alldata for any related TSB's? How are the motor mounts? Have you had the injectors cleaned?(not that pour in the tank crap) When did you replace the fuel filter? Have you tested the sparkplug wires? Have any vaccum hoses fallen off? What brand plugs were in it and what brand did you replace them with? If you have done all this, forget it and take to the dealer, it will cost less in the long run.

Because the sensor is NOT defective. You test procedure is defective.

-Philip

Per 1995 Camry Service manual for 1MZ-FE (V6): - disconnect the O2 sensor connector.

-Using an Ohm meter measure between terminals +B and HT.

-If resistance is not between 11 and 16 ohm at 68 degrees fahrenheit, replace the sensor.

When viewed looking into the connector - the top has three notches and the bottom has 2 notches. Upper left is +B and upper right is HT.

The only valid O2 sensor test is the dynamic response test performed by the car's onboard computer. Checking the O2 sensor's heating element is not a complete test.