Auto Parts: 03 Toyota corolla - O2 sensor extension, threshold bank, o2 sensor

Question
QUESTION: Hi Greg, Have an '03 corolla showing code P0420, Catalyst efficiency below threshold(bank 1 sensor 1).  This i belive is the sensor just in front of cat converter.  So, i want to test it, but the socket that connects the sensor to wiring harness, has some insulators in back of socket, so i don't want to back-probe and mess up what is there.  Also don't really want to splice the wires.  I've seen extensions for other cars.  It would have the male and female halves of the socket.  Do you know if they have one for this?  It has 4 wires, and the socket has 4 flat, horizontally positioned prongs.  They are lined up 2 x 2, so 2 over top of 2.  If i could get just the male and female socket halves, then i could make my own extension/harness for testing.  Maybe there's an easier way?

ANSWER: Ron. Let me do a check on an extension for you. However, I feel that this may be a case where there is a problem purely with the converter itself. I will get back to you shortly. Thanks.
Greg

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QUESTION: Thanks Greg,  if you can't find that, i was thinking of bench testing the sensor.  ACcording to the instructions at this page, http://www.mr2.com/TEXT/O2_Sensor.html, i'm just confused about testing, bcz it's a 4 wire sensor.  So, is connecting the wires as he says good, or do i also need to supply 12 volts to the supply wire on sensor?  Thanks a lot.

Answer
Sorry it took a couple days Ron. The only way I have tested these is with an OHM meter. Measuring the resistance works for most sensors. It sounds like your O2 sensor is heated by it being a 4 wire. That would be the only thing I would put a supply on. Not the sensor itself. Hope this helps and Happy Holidays. Greg