Replacing front O2 sensor on a 2000.

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Which O2 sensor are you replacing, the front or rear?

I just replaced the rear on my 2000 and it was pretty straightforward.

Some pics would help.
 
Nelsonmd said:
Which O2 sensor are you replacing, the front or rear?

I just replaced the rear on my 2000 and it was pretty straightforward.

Some pics would help.
Click to expand...

The front. I don't have any pics, but the front one comes out of the exhaust and then the other end of it is somewhere up above the crankcase, in a place where my hand won't go. If I can get some pics with my old camera (doesn't take closeups too well), I'll post them here.
 
when you say "disappears up over crankcase" are you describing where the wires from the sensor lead to the harness or are you talking about the sensor, itself?

My front sensor was difficult to remove simply because the harness was a PITA to access, though keep in mind your situation could be different since you have 2 cats (to my 1) and an auto tranny... i think
 
denverunner said:
when you say "disappears up over crankcase" are you describing where the wires from the sensor lead to the harness or are you talking about the sensor, itself?

My front sensor was difficult to remove simply because the harness was a PITA to access, though keep in mind your situation could be different since you have 2 cats (to my 1) and an auto tranny... i think
Click to expand...

The wires from the sensor lead to the harness which is somewhere above the crankcase. I have a manual tranny, btw. I now have a pic.
P1010628Small.jpg~original
 
Wasatch Rebel said:
The wires from the sensor lead to the harness which is somewhere above the crankcase. I have a manual tranny, btw. I now have a pic.
P1010628Small.jpg~original
Click to expand...

Okay, the harness is back up under there and a PITA to disconnect (in my experience) I hugged the tranny (gross) so i could use both hands to disconnect the old one and plug in the new one.
 
denverunner said:
Okay, the harness is back up under there and a PITA to disconnect (in my experience) I hugged the tranny (gross) so i could use both hands to disconnect the old one and plug in the new one.
Click to expand...

I'll give it another try. I tried to stick my hand up in there, but couldn't find the end of the harness. But maybe I need to work at it a little harder. Better than paying someone big bucks to do it for me. So, what did you do, reach up in there, unplug the old one, then keep a hold of the plug and stick the new one in there? I'm thinking I may get the old one out, but then not be able to find the plug again for the new one. Crap--that is a PITA!
 
yeah it's frustrating. I sorta used a long flathead driver to help unclip the harness. Clipping in the new O2 sensor to the harness is more difficult than pulling it apart.

This site has a good writeup/reference..

4Runners.org - Changing Your 02 Sensors

unfortunately, it didn't help much with accessing the harness (imo). You'll get it eventually! Took me a lot longer than I ever thought it would!
 
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Yeah, these things are a surprising pain to unplug. Try practicing once or twice on your rear sensor before trying the front one blind. This will help alot.
 
Don't try to unclip the harness first on the front sensor on a Cali. or '01+ two-cat system. Unbolt the sensor FIRST, pass it over the top, and it will hang down the other side and you can easily unclip it. Same thing to reinstall: Do the plug first on the other side, pass it over the top, then bolt it in. The write-ups were all done on one-cat systems where you can get to the plug and don't need this trick--so they have you unclip the harness first. Drove me nuts until I tried it the other way around--then it was a piece of cake.

Disclaimer: this works on my 'Cali. '99 manual. Not sure if this applies to auto trans.
 
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Wasatch Rebel said:
I'll give it another try. I tried to stick my hand up in there, but couldn't find the end of the harness. But maybe I need to work at it a little harder. Better than paying someone big bucks to do it for me. So, what did you do, reach up in there, unplug the old one, then keep a hold of the plug and stick the new one in there? I'm thinking I may get the old one out, but then not be able to find the plug again for the new one. Crap--that is a PITA!
Click to expand...
Hey I'm having the same problem! How did you end up disconnecting the plug on the front sensor?
 
NathanOfSeattle said:
Thank you, but what exactly do you mean by "pass it over the top"?

Also, how do I know if my car is Cali spec? Would I have more O2 sensors if it were?
Click to expand...

Just unbolt the sensor and stick it back up where the wire comes from. It will fall down loose on the other side (of the trans or whatever's in the way, I'd have to go look at the truck to be exact). Cali spec will say California on the emissions label under the hood, and it will have two cats. It would not have more sensors, all 3 Gens have one front sensor and one rear sensor. But if you can't get to the connector, that pretty much guarantees it IS a Cali.
 
TheDurk said:
Just unbolt the sensor and stick it back up where the wire comes from. It will fall down loose on the other side (of the trans or whatever's in the way, I'd have to go look at the truck to be exact). Cali spec will say California on the emissions label under the hood, and it will have two cats. It would not have more sensors, all 3 Gens have one front sensor and one rear sensor. But if you can't get to the connector, that pretty much guarantees it IS a Cali.
Click to expand...
Thanks, I will try that tomorrow morning.

Regarding the California emissions, what exactly do I look for under the hood? Sorry, I don't go down there that often and have no idea what to look for.
 
koulee said:
Its a label on the underside of the hood describing its emissions standards that it has to meet.
Click to expand...
I checked real quick and to paraphrase, it says that it meets all US states and including California regulations. So I guess its all emissions rather than just CA emissions?
 
TheDurk said:
Just unbolt the sensor and stick it back up where the wire comes from. It will fall down loose on the other side (of the trans or whatever's in the way, I'd have to go look at the truck to be exact). Cali spec will say California on the emissions label under the hood, and it will have two cats. It would not have more sensors, all 3 Gens have one front sensor and one rear sensor. But if you can't get to the connector, that pretty much guarantees it IS a Cali.
Click to expand...

So I tried your technique. Didn't really fall down loose on the other side. And I still could not reach the plug. It feels like the plug is clipped into something up top. I think maybe your technique may not work for a 2000 4runner. Thanks though. I may just have to pay my mechanic to do it for me.
 
NathanOfSeattle said:
So I tried your technique. Didn't really fall down loose on the other side. And I still could not reach the plug. It feels like the plug is clipped into something up top. I think maybe your technique may not work for a 2000 4runner. Thanks though. I may just have to pay my mechanic to do it for me.
Click to expand...

Sorry about that...I thought it would be the same as my '99 Cali.
 
love the passing it over the top approach

"Don't try to unclip the harness first on the front sensor on a Cali. or '01+ two-cat system. Unbolt the sensor FIRST, pass it over the top, and it will hang down the other side and you can easily unclip it."

Tried this. Works great!!
 
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