Hi all , New to forum. I am trying to get a 2000 Montero sport 3.0 (federal) going . We started it up the other day after it sat for a few months. Wow was it loud--put my hand on exhaust and WTF no exhaust--crawled under to find someone cut out the cat--had an aftermarket cat put in. So the theives cut after the O2 sensor -so we have one o2 sensor pre cat and maybe they cut the wires or something for the second 02 sensor--but I can't find anything-- does anyone know how many 02 sensors I should have and where they might be located. The Internet is all over the place with some saying 4 sensors some saying 3 and some saying 2--HELP!

 

Monteros do come with ether 4 or 3 O2 sensors. It all depends on year of manufacturing. Based on the model year, I'd venture to guess you should have 4 of them
However, all 4 should be located ahead of your main big catalytic converter. The first pair will be on each side of the engine, just after exhaust manifold (tucked right by the wheel wells). The other two will be further down after smaller cat converters located on the Y-pipe. One is near front driveshaft, second one more near the center of the engine/transmission mating area. The connectors for those back O2s are located on the side of transmission. I think the exhaust pipe runs right along there, so there is a chance that wiring was damaged ether by saws or by welding new cat.

 

Here's a diagram from 2003 Montero Sport. Your 2000 MS should be very similar. The O2 sensors are #11. With four of them on the left side (just after the engine). I hope this helps.

 

So crawled under and looked based on diagram--it looks like I have no 02 sensors were the diagram says I should I can only find one before the cat--totaly baffled

 

Post couple of pics from below and from above along the sides of the engine

 

tried to post pics--no go

 

If photos are too large, save them to Google Drive, Google Photos or some other online storage. Then share a link

 

 

trying

 

Completely stumped. I see only one O2 sensor in all those photos.
I pulled another diagram from the parts suppluer I often use. This one shows just a single O2 sensor after the Y. I wonder if this is setup you might have? At the same time, same supplier shows a 2000 Montero Sport with all 4 sensors. Did they make multiple versions in the same model year? Don't know, but I've seen that kind of thing in VW. Where same model year vehicle built at different factories were different

not interchangeable.