Ok so I bought my truck and the guy before me had new exhaust put on. He pulled out the cat and put in true dual with flowmaster mufflers. He took the o2 sensor out and just taped it to the frame. It sounds really good but the only problem is the check engine light comes on and tries to flood out my motor. It has reduced my gas mileage and power as well. The light only comes on when the truck has warmed up and when I read it the light it said there was a problem with the o2 sensor. I tried using a spark plug defouler and plugging it with a bolt but that didn't work. I also tried buying and o2 cheater but that didn't work either. I know there is a way to bypass it and make the ecu run fine without the o2 sensor but I can't remember how to do it and I've gotten out of touch with the guys that I know that did it. How can I get rid of the check engine light without putting in another cat?

 

Which o2 sensor? If it's the precat o2 there is nothing you can buy to fool it. In either case, get them reinstalled to the exhaust system properly. A muffler shop can weld new bungs into the pipe.

 

i see you have a 95 which i think is a one O2 system (OBD I). you need to have an H pipe or an X pipe welded in, with the O2 installed in that section. the previous owner was a dumb ***.

in your situation, some people will install the O2 in just one side of the true duals and hope for the best. that will work, but the pcm is basing the fuel trim on that one side, its not the right way to do it, but it will work.

 

I could try the H-pipe or X-pipe. It's a post cat though so wouldn't it still be sending a bad signal to the ECU? It's not so much a problem getting it in the pipe that I'm worried about the question is will I still have a check engine light if I was to just put the sensor into a pipe without a cat? I'm pretty sure I would so I was asking if there is a way to "fool" the o2 sensor or ECU.

 

You shouldn't have a post-cat sensor on your truck....... that will certainly skew the readings. Your system originally had one sensor, at the front of the cat. You don't need the cat, you DO need that sensor in the exhaust stream, taped to the frame does you no good at all... (there is LOTS of oxygen there....... which the sensor will see as an extremely lean condition....) Even reading just one bank will be better than what you have now.... If the pipes are run parallel down one side of the truck, (not one pipe down each side) you can just weld in a very short H or X pipe, and put the sensor right in the middle of that.

 

It is very possible he has a late 95, and two o2 sensors. If this is the case and you are sure it's the post cat sensor, then just leave it where it is. The post cat o2 will not cause the motor to flood out. If it's the pre cat sensor, replace with new. And what is the code # when you check? A little better info would be nice too, I'm not into guessing.

 

ok lets start over.
how many o2 sensors does your truck have?
where is the pre-cat o2 sensor installed?
have you replaced it yet?
what CEL codes do you have?

 

It has one o2 sensor. I assumed it was post cat because I asked a friend that has a 98 and his is post(or at least he said it was). the pre-cat o2 sensor was taken out before I got the truck. It was taped to the frame. I have not replaced it. I tried buying a "o2 cheater" and it didn't work. With the cheater installed I'm getting a reading saying that the air/fuel mixture is too rich. It's also giving me one that the o2 sensor is sending a faulty signal. I also got a "37" but I don't know what that is because the manual I have doesn't have a "37" for my truck. If it really is a pre-cat then I will just have it put in on one side and call it that. My manual doesn't say.

 

Your friend with the 98 has two O2 sensors. One pre-, and one post-cat. Since you only have one, it is pre-cat. running off of just one side should work. I think.