ok heres the deal im looking at getting a test pipe to replace my cat due to the fact that i live in a state with no emission laws. but the problem is that once i put it on my check engine light will be on anybody know how to fix this without having the ecu chipped thanks.

get an 02 simulator

What actually makes it throw a code, the cat missing, or an O2 sensor?

o2 sensor

well then call me crazy but why don't you modify the test pipe to hold the O2 sensor.

It's the absence of the cat that throws the 02 sensor off. You get an 02 sim so that it sends the ECU the right reading so that it doesn't give you a CEL and throw an error code.

Sounds like that the simplest fix could be to solder a resistor in to keep from throwing the code. I would have to get my hands on the schematics for it or figure out the voltages it uses to throw the codes and what makes the ecu determine a code, but I'm pretty sure that's all it would take.

Sounds like that the simplest fix could be to solder a resistor in to keep from throwing the code. I would have to get my hands on the schematics for it or figure out the voltages it uses to throw the codes and what makes the ecu determine a code, but I'm pretty sure that's all it would take.

ask zip22 from clubsi.com for the info on that. also, he sells o2 sims.

he is also a mod there.

You need a sim. What throws the code is there are two sensors (at least) one before the cat and on after the cat. They a set to read within a certain amount of whatever they counts. If the front one reads the same and the back one reads irregular, the light will come on. I would not worry about the light. Just check your codes every once in awhile to make sure a new cod does not pop up.

You need a sim. What throws the code is there are two sensors (at least) one before the cat and on after the cat. They a set to read within a certain amount of whatever they counts. If the front one reads the same and the back one reads irregular, the light will come on. I would not worry about the light. Just check your codes every once in awhile to make sure a new cod does not pop up.

actually, the primary and secondary are independent of one another.

well looking more into it i dont have an o2 sensor after my cat just before so i dont know if that will make a differance

well if your car is pre-obd 2....u wont have a Secondary o2 sensor....just a pre-cat or "upstream" sensor....u can either make an o2 simulator, or if your car is obd 2, buy an obd-1 conversion harness, and an obd-1 ecu....might as well get a chipped or "pre-programed" ecu for your ride....as for the way o2 sensors are related....they are some what...and then again aren't....both o2 sensors need to be working with each other to know if the cat is working....the upstream o2 sensor reads what is coming out the head, typically between .1-.9v's, (lean/rich), and the downstream(after-cat) reads cat eff. aprox. .5v's +/- .1v's. if either sensor is incorrect, you'll recieve a code....2 diffrent sensors....some what related...but not