I have an 03 Dakota 3.9 v6. My truck has 3 cats. 2 pre-cats and the main. The two pre-cats have the oxygen sensors directly in the end of the cats, upstream and down stream of the main body. The passenger pre-cat and main cat have gone bad. The new replacement from dodge is $900+. If I put an aftermarket system on and just had the O2 sensors installed in the pipe just before and just after the new pre-cats would this still give the computer the information it needs on the mixture diff? I am working with an exhaust shop to work something out and save some money and increase performance a little. No one seams to make any cats that have O2 sensor directly in the ends of the cat (other than dealership).
Does anyone know if I can alter the placement of the O2 sensors by a couple of inches?Thank you,

Brian

 

welcome to DF...

the upstream o2's need to be right off the collectors and the post cat o2's are only there to monitor the cat effeciency. you can move them and you should be fine. as long as the pre-cat o2's are before the cats...

 

just cut early so the sensors stay on the pipe. and weld the cat in there that way you don't need anything like that, alternatively you could find a set of nuts that fit the sensors and cut a small hole in the pipe big enough for the nut. Just weld the nut in the hole, but best would be to just do the cuts early/late to keep them in.