Need some help with Oxygen (O2) sensors

[josh40601]

Hello everyone, I have to add O2 sensors to my truck and I need to know where they were located from the factory, but I also think I may have problem with my current exhaust setup.

I found some info in this thread http://www.explorerforum.com/forums/showthread.php?t=320348&page=3

when the engine was installed, it didn't have anything past the exhaust manifolds, so I put a set of 2.25" pipe into a Y and a single Hi Flow magnaflow cat with another pipe to a generic turbo muffler then a turn down.

Plan was to put the 2 upstream in the new pipe in front of the cat, and the downstream behind the cat, but from what I was reading in that thread, the 302 has 4 sensors instead of the V6 which has 3.

Can anyone assist?

 

[1997XLTRollover]

Drivers upsteam is on the front left of the trans hanging down the bellhousing; the other 3 are up on top of the transmission. Without a stock pipe it's hard to tell which downstream goes where, but the upstream plug will be green and downstreams are blue. There's also a different notch in the up vs down plugs as well as different color.

 

[josh40601]

Drivers upsteam is on the front left of the trans hanging down the bellhousing; the other 3 are up on top of the transmission. Without a stock pipe it's hard to tell which downstream goes where, but the upstream plug will be green and downstreams are blue. There's also a different notch in the up vs down plugs as well as different color.

really? are you referring to the female plug? The only difference I have found between the replacement 02 sensors is the length of the wires


Also, forgive me for not clarifying... I'm asking where on the exhaust pipe the sensors are located, not the harness.

 

[1997XLTRollover]

really? are you referring to the female plug? The only difference I have found between the replacement 02 sensors is the length of the wires


Also, forgive me for not clarifying... I'm asking where on the exhaust pipe the sensors are located, not the harness.

Ah. Sorry. The bungs are right before and right after the first pair of cats on all non CA emissions vehicles. The only exception is the drivers side upstream which is right after the turn on the downpipe. If you're CA emissions I would think the downstreams would be after the second pair of cats but they could be after the third too I'm not really 100% sure.

 

[decipha]

i take it you don't have to comply with emissions where you are? if not then don't even worry about the downstream after cat hegos

simply replace the two front hego's, if you have to put bungs in it then you want them on the top half of the pipe, envision the pipe filled half way with water, you don't want them to get wet

you can either trace or ohm out the wiring from the connectors to the ecu connector to figure out which is which, worse case your trims split and your engine runs funky then you know you've got them backwards

 

[josh40601]

Ah. Sorry. The bungs are right before and right after the first pair of cats on all non CA emissions vehicles. The only exception is the drivers side upstream which is right after the turn on the downpipe. If you're CA emissions I would think the downstreams would be after the second pair of cats but they could be after the third too I'm not really 100% sure.

Thanks for the info. The truck is currently not a CA emission vehicle.

i take it you don't have to comply with emissions where you are? if not then don't even worry about the downstream after cat hegos

simply replace the two front hego's, if you have to put bungs in it then you want them on the top half of the pipe, envision the pipe filled half way with water, you don't want them to get wet

you can either trace or ohm out the wiring from the connectors to the ecu connector to figure out which is which, worse case your trims split and your engine runs funky then you know you've got them backwards

Not yet. I will in the future, but it is a 49 state vehicle, so that will help some. That's a different fiasco for a different day.

Thanks for the info. I've ordered a EVTM for the 97 explorer since the ECU/Harness/Engine/Trans all came from that vehicle. I think this will help me identify which 02 female plug relates to which location.