KwS 2425 Report post Posted April 25, 2014 Hi All, You some of you may have seen in my project thread, i discovered today that my M3 has had the Cats removed and replaced with resonators. I also noticed that both of the O2 sensors appear to be missing. There are two plugs tucked away next to the tans/drive shaft which i presume are for the O2 sensors. I dont have a CEL. My car is a late 1993 build. Being this early, does it need the O2 sensors, or could it have come without them? I dont know if the car has been coded to eliminate the O2 sensors. Removing the cats is OK as my car is too early to have post cat sensors, but having no pre-cat sensors is a mystery to me. Real OEM shows two sensors. If they have been removed, should i not have a CEL? Also, if i wanted to add then, can i? How can i tell if the DME has been coded to remove them? Quote Share this post Link to post Share on other sites
hybrid 1043 Report post Posted April 25, 2014 Car will be running open loop without them. It may or may not have had a tune on the open loop maps to kind of work. Probably not though. Only way to find out is to chuck it on the dyno with a mobile wideband up its pipe. The noobs who removed it would have done it when removing the cats and not had the bosses re welded back in. You cant really code them out so to speak its just that the DME is now in open loop mode (not very efficient and probably loosing a bit of power) Quote Share this post Link to post Share on other sites
KwS 2425 Report post Posted April 25, 2014 (edited) so in that case, it would be beneficial adding them back in, wouldnt it? If the DME hasnt been altered, shouldnt i have an error code or CEL? The car runs great, no soot on the bumper, and the economy would be in line with the way i drive it and the type of car it is. Edited April 25, 2014 by KwS Quote Share this post Link to post Share on other sites
KwS 2425 Report post Posted April 29, 2014 Any ideas? Should i look at adding the O2 sensors back in? The Previous owner has mentioned that no coding/flashing of the DME has been done, and the sensors were removed when the cats were removed. Quote Share this post Link to post Share on other sites
hybrid 1043 Report post Posted April 30, 2014 Put the O2 sensors back in. Pay careful attention to the stock position, angle and depth. Also they need to be put in the right way around EG left and right sensors. Should have different plugs if I remember correctly. Quote Share this post Link to post Share on other sites
