I have purchased a high flow catalytic converter that is a straight through race pipe design. After installing the high flow cat on my 2000 nissan maxima SE my check engine light came on. Why did it come on and what can i do about it. I know that there is more air flow but what can I do to prevent the light from coming on. I want to do a exhaust also but that will probably cause the light to come on too. Please someone help me because my car needs inspected and I am not sure if it will pass emissions. You can email me at ItalianStallion31@comcast.net. Please help me out. Thanks.

 

i think there is a sensor that needs installed on the test pipe

 

Where is the test pipe?

 

the test pipe is the same thing as the cat...thats what they call a straight thru pipe. i havent checked on our cats yet, but if the O2 sensor normally attaches to a part of the stock cat, then it would need to attach to some part of the new cat (test pipe)

 

Ok thanks. So there should be a way for the O2 sensor to attach to the cat then. Appreciate it. Also will a cat back system cause my check engine light to come on or no.

 

ODBII systems used on all cars since 95 use an O2 sensor before the cat and an O2 sensor after the cat. If the two sensors read the same, the ECU will assume the cat is not doing its job and will log an error making the check engine light come on. You might get by if you replace the downstream O2 sensor with a dummy sensor that reads a voltage in the middle of the normal range.

 

Now my check engine light is on with the code of PO135 what can I do or what is the problem now. Please help me out. It only happen since i changed the cat converter to a high flow.