I have a test pipe with one spark plug fouler. I was still getting the check engine light so I went to replace the 02 sensor. The old one was all nasty and black. I found a black box that was wired into the 02 sensor that goes into the test pipe. Just anothe surprise found from the previous owner. If the wiring or the box is bad could it cause the CEL?

I recieved P0142 and P170. Running rich and 02 sensor. Can I get some feedback or input on this please. I just got a stock cat to put back on to see if the light still comes back on. I don't want to lose the test pipe but the light is really annoying.

 

I thought it was 2 spark plug foulers...hmm...I used 2.

 

Someone told me I would be fine with one but two is recommended. I just wanted to know if the box they have hooked up, could be the cause for the CEL? I guess I can always try two and see what happens, can't hurt.