Toyota Repair: 98 Camry V6, voltage waveforms, o2 sensors

Question
I said in my previous email that the car was giving a code P0420 and after reading your previous comments would have someone change the Bank 1 cat. Our guy at work had the scanner on my car, because after 300+ miles and dozens of start and stops,long (60+) mile drives the cat readiness test still shows incomplete, yet no codes and a PASS on the scanner.
He checked the O2 sensors with the car off,
O2SV12= .001
O2SV21= .665
O2SV22= .665
He checked the O2 sensors with the car running,
O2SV12= .070
O2SV21= .667 =/- .003
O2SV22= .665 =/- .003
Could this be an intermittent problem with the O2 sensor or wiring? The car has 165K and the sensors have never been replaced. Any help you can offer would be appreciated.

Kris

Answer
If the cat monitor shows incomplete it will give a "PASS" this is not the case, the cat monitor must show complete for it to either show pass or fail. In most cases an O2 sensor failure will give a different code not PO420, the 420 code is a code specific to the cat converter's inefficiency. The cat efficency of the cat can be checked by monitoring both the O2 sensors in front and rear of the converter with a scantool that can display the voltage waveforms of the two sensors, the first sensor should have a waveform varying from +1v to -.5v with ,5v being the reference voltage, this is with the engine warmed up and running at 2000 rpm for about 90 seconds. The rear O2 sensor should be pretty much a flatline with a voltage reading of about -.6 or .7v, if the rear O2 sensor follows the front sensor's pattern then the cat is not working.