Cats gone, need to fool computer/02 sensors

[Butch]

when the o2s are gone or not working properly the A/F ratio will be changed. The vehicles have set tables to use when the 02s go out, kinda like a safe mode.

I messed up my original statement, when the rear O2s throw a code it means the Cats have gone bad and does nothing to the a/f ratio, when the forward O2's throw a code it means the sensors themselves have gone bad and that will play with the air/fuel mix

 

[CodyB]

Also, my local muffler shop, uses rear O2 threaded extensions a lot, I have used them a couple of times with good luck. They just move the O2 sensor up further from the exhaust stream and it fools the sensor in to thinking that the cat is still there. You can go to a part's store and get a pair of Spark plug non foulers from the help section make sure you get the 18mm ones, take them and drill the small hole open in them, and they work perfect, I actually keep some in my toolbox just in case someone needs one. I have been buying locally for about $8 for a pair.

This does work, however the factory AC Delco O2 sensors I had were too large, so I had to find a newer set of O2's to do this with. You drill the hole out to 1/2" on only 1 of the two, then thread two of them together per O2 sensor so its in the fashion of Pipe bung>unaltered spark plug non fouler>drilled out non fouler>O2 sensor. That does work whereas an electronic method does not work all the time, I have tried the resistor capacitor method.

 

[Aloicious]

dont waste your time with resistors, sims, drilling, or extensions...just get a tune to eliminate them if you want them gone. it will stop the SES light, it will do everything. and on top of that you can get the PCM tuned better all around.

and since there seems to be some possibly confusing info. there are 2 kinds of factory O2 sensors, those before the cats, and those after the cats. if you have both in your truck, the post cat sensors are the ones you can eliminate, what they do is monitor the catylitic converter efficiency and really don't have an effect on the A/F ratio or drivability. the pre-cat sensors on the other hand are directly responsible for monitoring and altering the air fuel ratio and will result in problems, and drivability issues if they are removed... there are reasons to remove the pre-cat O2 sensors and only run in open loop, but there's no reason to go into that here. and there's no reason to do so unless you're doing some OL tuning yourself.

with that said, get a tune. if you absolutely don't want to get a tune, you can just run without the post cat O2 sensors, it will throw a SES light on all the time, but it will not affect drivability. but personally, I'd rather have the SES light be usefull and actually tell me when something is wrong, rather than just having it on all the time because of something like this.