I am trying to find the pre-cat O2 sensor for my truck and I notice that all of the sites ive looked at say either "right upstream" or "left upstream" in the description, but my truck only has one before the cat. The cat acts like a Y pipe and is single exhaust from there back, I am planning on getting rid of it and making it full dual exhaust tomorrow but I also need to replace the O2.

Thanks

 

Make sure you get an NGK or NTK brand o2 sensor. It shouldn't matter, I don't think, whether you get left or right...but go with right (meaning passenger side) upstream o2 just to be safe.

The best way with true duals is to have an H (or x) pipe and put the o2 on that instead of before or after.

 

Figure out how long the lead is on your O2, they sell both an 18" and a 12". Left or right designation doesn't matter.

 

the actual O2 sensors are all the same - heated O2, 4 wire.

what you need to decide is whether to use a universal (4 leads, no connector)
or an exact fit (length of leads, and specific plug)

there are 2 lengths - long (18") and short (12")
there are 2 electrical plugs, round and square.

i attempted to get exact fit, and ended up with the wrong shape plug, so i cut off the plug and spliced on my old plug. i'd been better off buying a universal and saving $10.

if you want to use an exact fit, then unplug your old O2, check plug shape (round vs square) and measure how long it needs to be. both front and rear O2 plugs are up on top of the trans/tcase area. they are attached by a plastic stud. i cut the stud off to remove, then just zip tied the new ones back into the old hole where the stud was.

why is it so complicated? i don't know, but the application guides are wrong for our trucks. california emissions had 4 O2, federal emission had 2. why 2 shapes? i don't know.

 

Thanks Matt,
thats one thing ive been trying to find out about too is where do I put the H pipe, Ive heard that some people wait to see where the pipes are heating up and then connect it to those two points or something like that. or should I just put it at the closest practical point i can toward the engine? Also I assume the length of the H pipe is supposed to be as short as possible?

 

I spent about 30min under the truck last weekend trying to unplug the damn connector for that O2 sensor and then I discovered if I go inside the truck and remove the boot for the t-case shifter that I can access it pretty easily.

 

i CAREFULLY cut the plastic anchor stud with a pair of side cutters, then dropped the wiring down where i could see it, and separated the connector.