I'll try to keep this as short as possible. Got the P0136 code and decided I'd go ahead and replace both of my O2 sensors. Ordered the parts (front:234-4161, rear:234-4154) and was able to get under the truck to get the job done about an hour ago. What I found has me a bit baffled.

I bookmarked two write-ups with photos from 4x4wire.com and 4runners.org which describe the process and it seems fairy straight forward. My problem came when I looked at my front sensor and found that it doesn't look like the photos on either of those two sites. Both URD and Denso list the front sensor part# as 234-4161, but it doesn't look like the wire going to the plug is going to be long enough. The damn thing on my truck goes up and disappears above the transmission. What the?!?

I've searched on here with no luck finding an answer as to why this is the case, or found anyone else who mentions this type of sensor. The only thing I found was one post that alluded to a part number that both Denso and URD get wrong because the wire isn't long enough.

Does anyone know if it's possible to cut the wires going to the old plug and solder the wires from my new sensor?

Here is a crappy cell phone picture showing what I mean:
http://imageshack.us/photo/my-images...312163200.jpg/

 

Well, on my rig, the only way to change the front sensor is to unbolt the sensor first and pass it up over the top and then when it hangs down the other side you can access the plug and disconnect it. None of the DIY's I have seen talk about the two-cat system and the need to do this. This might be your problem.

This is the case on the two-cat system found on '99 and '00 Cali. v6 rigs and all '01-'02 trucks sold in the US. These all use a wideband O2 sensor in front and 234-4161 is a normal O2 sensor. So I have to ask, how many cats do you have? Is yours a CA (as in Canada) or US rig? What year? I have no idea if the two-cat system was ever sold in Canada, but I think you should rule this out by counting cats.

In any case, you might try unbolting the sensor and passing it over the top. Then see if you can unplug your old sensor and plug your new sensor in. The plugs on A/F sensors and O2 sensors are different, so the wrong one won't fit.

 

It's a 98 Canadian rig, and it only has one cat. I'm a little confused because the 234-4161 doesn't seem to have a long enough wire between the sensor and plug for it to reach up above the transmission where the plug is. But everywhere I look the only sensor listed for my year, transmission and engine is the one I have. I need to call the stealership tomorrow to order some new nuts for the sensors and I'll ask them what the correct part number is for the front sensor.

 

And another thing...what is that metal pipe that the sensor plug in this picture is bolted to?
http://www.4x4wire.com/toyota/4Runne...20location.jpg

It's missing in the picture in my original post.

 

In the second pic, it looks like the auto transmission fluid line up to the cooler. Or, some other fluid line.

 

If its the original sensor you may be able to clean up the body enough to get a part number off of. And yes you can cut and extend the wires to the sensor as long as you match them correctly.

 

that is just a clip bolted onto an atf line elbow
specifically to hold the sensor wire up.