o2 sensor

I have a 2001 Ram Offroad with a 5.9. Replaced the y pipe, cat and the tube behind the cat. Replaced the front o2 sensor. The problem I have is I can not find the correct o2 sensor for the rear. First visit to the auto part store they gave me a sensor with a round fitting. Not the right one. Exchanged that and they gave me a square fitting, still won"t fit. I have taken a pic of the end so maybe someone ran into the same problem. Thanks

Before you replace it, clean your original with oven cleaner and put it back in.

If, for some reason that won't work, get one from Mopar. It might cost you another few dollars but it's worth it. Those sensors measure in millivolts and most of that aftermarket, Jobber garbage doesn't cut the mustard and eff's things up as you can see already.

Been there, done that.

FWIW, I have an '01 Off-Road 360 and have only cleaned my sensors once in over 200,000 miles.