ak4rnr

I'm hoping this post will assist others who have a 2000 4Runner 4WD, non-CA emissions, manual (5spd) that needs its 02 Sensor replaced.

My 2000 4Runner had 153k on it and I'm guessing that the 02 sensor (at least on a non-CA emissions this is the sensor located in front (upstream) of the single catalytic converter) had never been changed. I searched quite a bit on this site, as well as others, but didn't realize that, at the time, there is a pretty big difference between an automatic and a manual as to where the actual 02 sensor plugs into the vehicle!

For the most part, you can use other posts on this site to figure out how to take off stubborn/rusted exhaust sensor stud nuts; that won't really vary as to whether it's a manual or automatic. However, the 02 sensor pigtail connection for a 2000 4runner manual transmission (aka 5spd) is located above (on top of) the transmission just in front (closer to the front of the vehicle) of where the stick shift is. It just happens to be in one of the most inaccessible places on the vehicle

I spent much more time than I care to admit trying to figure out how to get this pigtail connection unplugged. (Hint: look at the other 02 sensor's connection, the one downstream from the catalytic converter, which is much easier to access and unplug and practice unplugging it so you know where the plastic clip is located on the pigtail connection!). For me, it worked best to take apart the shifter boot/cup-holder/parking brake lever trim pieces inside the vehicle, then have someone engage the release clip on the pigtail harness using needle nose pliers from within the vehicle, then, at the same time, have someone else go from underneath the vehicle and reach up between the transmission and the shifter and work the 02 sensor's pigtail connector loose by hand. So, in total, it took two people.

Over the many hours I spent trying this or that, I found that going for the 02 sensor's pigtail connection ONLY from the bottom of the vehicle (via the gap between the transmission and the shift stick area), or ONLY from within the cab (via removal of the shift boot/cup holders/etc.), resulted in futile attempts and bloodied knuckles. It wasn't until I had someone engage the release clip on the 02 sensor's pigtail connection using some needle nose pliers from within the cab at the SAME time that I was grabbing the pigtail connection from beneath the vehicle (you only have room for one hand in that area!), did it actually come off.

Hindsight being 20/20...had I done this from the beginning the entire job would have taken me ~ 1 - 2 hours, with most of that time spent getting the rusted nuts off the exhaust sensor studs (I had to use a Dremel with a small cutting wheel and cut one of the nuts off). However, battling the tight spaces, it took me waaaay longer than I care to admit to unplug the pigtail harness connection.

I used Denso P/N 234-4161 for my 2000 4Runner 4WD, manual (5spd), non-CA emissions (only one catalytic converter) for the 02 Sensor that is in front of (upstream) of the catalytic converter.

Hope this helps someone out!!

TheDurk

Sorry, but for the one-cat exhaust system the front sensor is a an O2 sensor, in ALL cases. If you don't believe me, look at your sticker under the hood. In the top left corner, under where it says ENGINE FAMILY, it will say: "....HO2S(2), TWC..." which means TWO Heated O2 Sensors, Three-Way Conveter). The two-cat systems that use the A/F sensor say: "A/F S, TWC(2), HO2S.

Second, the P/N is 234-4161 not 235-4161, and it is, indeed, an O2 sensor:

ak4rnr

Thanks TheDurk! I've made the corrections you suggested...I appreciate it!!

75w90mantraN

Ahh, unplugging that a/f sensor pigtail is a PTA on manuals. I gambled a couple years ago and patience is a virtue! Because the parking lot was empty and I had of course bet this was going to be a simple one like the rear. Man was I wrong!

Nice little write-up on your experience