O2 sensor replacement

Hello, first post on the forum.

I am trying to replace my bank one system one O2 sensor due to a 171 code and increasing stuttering at highway speeds.

I opened up the shifter boots to gain access to the wiring harness and I noticed there is an extra unplugged harness. I looked and looked and can't find where it plugs in to.

My question is, is it an extra harness plug for some reason or what?

 

Most likely the power to light the shifter on an automatic truck. Same harness may be used for both autos and sticks.

 

So it is supposed to just flap there and be unplugged?

 

The unplugged harness comes off a wire that comes from where the system one bank one O2 sensor plugs in. So I was wondering if this unplugged harness needs to be plugged in to then fix my CEL code and restore performance

I am kind of hoping that is the situation because the nuts holding the O2 sensor on are rusted round and don't want to come off without a fight

Any help is much appreciated!

My Haynes manual is not much help

Thanks

 

I guess I may not be following you. If you have a male and female plug and neither are connected, then you should try to see if they fit. Toyota makes their plugs different throughout the vehicle. If the plug can not fit into another plug, it doesn't go there, if it fits, then it belongs there.

 

I got one plug end , I think it's male , not sure, but I can't find the other plug to plug into.

My question is: is this normal for a 1999 3.4 Tacoma (I don't think it is) or does it plug into somewhere ( more likely)?

And do you have any idea where it plugs into?

Thanks for the help

 

There was another fella on here a while back asking about thst same plug. He too had no where for it to go...just an unused connector. Theres unused connectors all over your truck...

 

Yes sir, thanks that was what I was after!

So there are in fact unused connectors all over truck?

Can you link me to the other guys thread possibly?

Thanks again

 

Yes there will be unused connectors, toyota will use one harness but there are many different options you may or may not have, resulting in an unused connector. Im sure its pry for an automatic truck like mentioned above....

Cant even begin to remeber what thread that was where the guy was asking about that thing. I believe he was working on something else and happened to find connector and asked about it...

 

Copy that!

Now on to replacing the O2 sensor

If pb blaster and vise grips don't get the nuts off the exhaust pipe studs then I thinks it onto some precision grinder work...

Anybody know the nut size there for the O2 sensor? M8 1.25 I think?

Thanks again. I'm diggin tacomaworld!

 

A butane micro torch is your best friend for this job. Heat the nuts up red hot and they will turn right off vise grips. The job is a pain if you twist off the studs. You have to remove the entire Y pipe to fix it correctly.

You can use a regular propane torch, but the chances of setting something else on fire is possible.

I think the nut is a 12mm. It doesn't really matter, you wont likely be using a wrench anyways

 

Will a heat gun work? I only have a regular propane torch... Hmm.

I was going to buy some replacement nuts hopefully.

Yeah, they were 12 mms at one point, not anymore.

You generally use vise grips though because they get so rusted?

 

Yeah i "think" you are right on tje nut size..m8 1.25

 

Heat gun won't work. If you are skilled with the propane torch, that will work better than the micro torch. Vise grips are the way to go once the nut is red hot.

Just keep some water in a spray bottle hand for cooling down things that look like they are getting too hot.

 

I just did this job. I pried the old nuts off as much as possible with vice grips, then chased the threads with a die, then cleaned the whole area with a wire brush.

Bolts are 8mm x 1.25. I got new stainless lock nuts and installed a new sensor and new gasket along with.

 

Thanks koditten.

I'll update the progress / destruction! I mean progress

 

The old O2 sensor is off and the new one is on. Quite a bit better performance. But the CEL came right back on. I'm gonna check and see if it is 171 again.

I did use a propane torch and vise grips. It worked like you guys said it would. The whole replacement is kind of a pain.

I think I'll keep this thread going until I chase out that CEL.

Thanks again