I just tried to put my new Denso O2's in that I got from Rockauto, all the plugs for my specs were square so that's what I bought, but when I pulled the old ones they have round connectors. I also checked Oreilly's and Autozone and they show square connectors for my model too. I'm guessing I have '00 model wire harness? Anyone else have this issue when changing O2's? I have non Cali truck, Automatic, quad cab
Plug on the left is upstream, right: downstream

 

Yeah, Dodge used both style connectors, and so far as I can tell, there was no rhyme or reason behind which you have....... contact rock auto, they should be nice enough to just swap 'em out for ya.

 

I just changed my O2 sensor and I had the same problem. Turns out I have '00 model wire harness.

 

Thanks, I sent back the square ones and should have the new round ones next week. Only thing is the Upstream one I ordered is only available in 13" wire in stead of 18", I know it'll reach but hopefully it don't bother the PCM.

 

Upstream uses the shorter lead, as it doesn't have quite as far to go to its connector. It's all good.

 

as far as i know, the actual sensors are the same for the front/rear, left/right, round/square, and long lead/short lead. the important features are the number of wires and number of heaters. our trucks are 4 wire with 2 heaters.

i had the same connector mismatch problem, so i reused my old harness and just cut off the old O2 and spliced in the new O2 with butt connectors. that worked fine. if you want to spend the time, you could solder and heat shrink.

so i ended up spending a little extra money to avoid the universal O2, but then ending up making it into a universal anyway.

so -- just buy the universal to start with and save the money.