Toyota Repair: Multi-sensor failures, mass air flow sensor, air flow sensor

Question
I asked this question before but I can't ask the original person I guess.  


Specs: 2001 LE Corolla - Stick Shift - 117,000 miles In July the famous "Check Engine" light came on. It was the O2 sensor in front of the Cat. Converter, I replaced it. Two days later, light back on - Cat. Converter needs to be replaced. Replaced it along with rear 02 sensor as recommended with that replacement. And it continues, 1 week later, light on again - front O2 sensor failed - replaced again. Two weeks later - light again, Mass Air Flow sensor. Replaced it - lasted 2 days and fried it out, replaced again, fried out again. They determined it was not the part, but they had no idea what caused it. They sent the car to several shops and no one had ever seen this or had any clue what could cause this. After lots of opinions, they opted to replaced all of the sensors, the entire exhaust system including the Cat. converter. So, had the car a week and the ^%#$^% light came back on. I stopped at Auto-Zone today for a free diagnostic and it is the front O2 sensor again. I haven't called the repair shop yet, I'm sure they will love to hear from me!!! This is my third Toyota and I expected to get to at least 200,000 miles. I just am at a loss about what to do next. I thought maybe you had encountered this somewhere else. Thanks for any information you have, Angela

The code from Autozone was P0420 - just that one code


Thanks

Answer
P0420 is the post cat o2 sensor.
Hook the fucker up to a multi-meter & check it's output.
"After the engine is warmed up and the vehicle
driven for 5 min. at 32 – 80 km/h (20 – 50
mph), the waveforms of the heated oxygen
sensors, bank 1, 2 sensor 1 and bank 1 sensor 2
have the same amplitude.
Three–way catalytic converter
Open or short in heated oxygen sensor circuit
Heated oxygen sensor"

It's this simple babe. If the o2 sensor checks out. The cat is shot.







btw You haven't been using some odd for of gas have you??? Leaded? Alcohol blends? You would know alcohol blends as Gasohol.
Commonly touted now as E85 on newer car commercials.
(Gasohol = E85, E90, etc tells the ratio of alcohol to gas)