I have a 99 QC 4x4 5.9L, I purchases 3 new 02 sensors for it today. I went to throw them in and there is only one 02 sensor precat and it is directly into the cat just after the 2 pipes go into it. What the hell is going on I must have an old exhaust on my truck or something.. what do I do ?? can I just use one of the two NTK 02's i bought ?

 

#23151 is the one i used for my 97. It for the right side but it did call out for 2 but i crawled under to confirm and only one inside the cat right side.

 

2 O2's on federal emissions and 4 O2's on California only. For some reason, the application guides all seem wrong.

There are also 2 shapes of connectors. square vs round. application guide is wrong on those also. its best to unplug your old, note the shape of the plug and the length of the wire so you get the right ones.

 

well i through one of the new ones on same plug same length , will have to see if the light comes on or if it runs like shi*t