Can I disable the catalytic converter sensor on my wife's car?

Tester — <font color="blue" face="times><i>"Wouldn't it be easier just to repair the vehicle correctly?"
No. The OP could buy a secondary O2 sensor simulator for under $50 and install it himself in about 10 minutes. The OP wanted to save a few dollars.

My vote would be to fix it right and I’m not a fan of trying to trick the computer.

“The OP wanted to save a few dollars.”

But how much is he going to save, if he misses a CEL that is trying to tell him that something is wrong that could cause expensive damage to the engine. Without a functional CEL how would you know.

If the part cost only $50 and ten minutes time, let’s get it fixed.

The part that REALLY needs fixing is the catalytic converter…$300 and up…

Square wave output from an oxygen sensor?/ NOT! All you need is a simple voltage divider, a resistance bridge to provide the correct voltage to the ECU and the CEL stays off…

Using a spark plug non-fouler to spoof the downstream o2 sensor WILL work for p0420 or other “cat below efficiency” codes in many cases. It’s going to cost you $5, about 20 minutes of work, and it’s a non-electronic solution. However as other folks have mentioned here, it would best to fix the car correctly, including repairing any misfire situation that caused the cat to begin to fail in the first place. It also may be illegal in your state. All of that said, for a borderline cat and a boderline money situation (I was broke when I first got married too), I’d say go for it. I actually still have one on one of my vehicles that has a really sensitive engine management system and my MIL has been off for 3 years+ AND the car still passes the emissions testing in my state all day long with low hydrocarbon and NOX readings. Good luck.

Well, I put my wife’s car on the scantool the other day and read the codes. It was the “cat below efficiency” that kicked the code, but then I watched the waveforms from the O2 sensors and recorded the numbers to look up later on the internet at the site that “mountainbike” mentioned. This was very helpful, as the upstream sensor waves were lazy and inconsistent even when the car was well warmed up. They never did reach higher than 85 mv or lower than 13 mv. Sometimes they would flatten out for a little bit. The downstream one I may wait to replace till I see if the waveforms become regular and help the lower one to perform better if the cat is working. Anyway, I’ve decided that considering the miles on the car, I should change them just for maintenance. The CEL has stayed off for over a week now. I’ve sure learned a lot about this from all you people.