How to change o2 sensor
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Chuckles89
New member
It's really simple. Just two studs in the exhaust piping hold them in. Just take off the two nuts and unplug the wiring connector.
MONTYMTB
New member
jeremyc74
Banned
It was mentioned in that thread, but I'll say it again here because I just had the same problem with one of mine (although not quite that bad), but spray it down with penetrating oil well before you start the work and that will help a lot.
I was able to drive a socket one size to small onto mine with a hammer and break it loose. The rear sensor was actually rusted much worse than the front one.
I was able to drive a socket one size to small onto mine with a hammer and break it loose. The rear sensor was actually rusted much worse than the front one.
gamefreakgc
Elite Member
It's not too hard at all, I'm sure you could do it.
Let your 4Runner cool down to be able to touch the exhaust components without burning yourself. Makes this less painful. You're looking for the first sensor on the exhaust pipe coming down from the engine. There's two: one before the catalytic converter and one after. You want the upstream sensor. It'll look something like this:
The sensor itself is secured by two 12 mm nuts. You'll need a deep socket or O2 sensor socket to take it off. I do not recommend using any sort of adjustable wrench or standard wrench since these nuts strip very easy. If it doesn't come off with reasonable force, use a liquid penetrant such as CRC's Freeze Off or Liquid Wrench, you can buy these at your local auto shop.
Once you get the sensor nuts off, the sensor slips right out. There's a old gasket probably stuck to the exhaust pipe, take this off as well. If chunks of it are left behind, lightly scrape it off but don't damage the pipe surface. You want this surface to be as smooth as possible to prevent any exhaust leaks.
You'll have to disconnect the O2 sensor wire from the main wiring harness. Follow the wire up until you find the connector. Disconnect using a pair of pliers or by hand if you can. Just be sure not to damage the receiving end of the connector (the old sensor doesn't matter).
Now just plug in your new one and start tightening back down the nuts. If the old nuts are damaged or rusted out, I recommend getting some new ones. Take them to an auto parts store or hardware store and have them match them. Torque the new ones to 14 lbs/ft. If you don't have a torque wrench, this is just snugged tight so it doesn't come loose. Any tighter and you risk stripping the thread.
Let your 4Runner cool down to be able to touch the exhaust components without burning yourself. Makes this less painful. You're looking for the first sensor on the exhaust pipe coming down from the engine. There's two: one before the catalytic converter and one after. You want the upstream sensor. It'll look something like this:
The sensor itself is secured by two 12 mm nuts. You'll need a deep socket or O2 sensor socket to take it off. I do not recommend using any sort of adjustable wrench or standard wrench since these nuts strip very easy. If it doesn't come off with reasonable force, use a liquid penetrant such as CRC's Freeze Off or Liquid Wrench, you can buy these at your local auto shop.
Once you get the sensor nuts off, the sensor slips right out. There's a old gasket probably stuck to the exhaust pipe, take this off as well. If chunks of it are left behind, lightly scrape it off but don't damage the pipe surface. You want this surface to be as smooth as possible to prevent any exhaust leaks.
You'll have to disconnect the O2 sensor wire from the main wiring harness. Follow the wire up until you find the connector. Disconnect using a pair of pliers or by hand if you can. Just be sure not to damage the receiving end of the connector (the old sensor doesn't matter).
Now just plug in your new one and start tightening back down the nuts. If the old nuts are damaged or rusted out, I recommend getting some new ones. Take them to an auto parts store or hardware store and have them match them. Torque the new ones to 14 lbs/ft. If you don't have a torque wrench, this is just snugged tight so it doesn't come loose. Any tighter and you risk stripping the thread.
Im new here but didn't know there was a 4runner doctor on duty LOLLLLL!
Correct me if Im wrong: I thought there was 2 oxygen sensors total on the truck (1 before the engine and 1 after).
Are you saying that there's actually 2 sensors after the engine (on the exhaust pipe) ?
thanks a lot btw
Pat
Correct me if Im wrong: I thought there was 2 oxygen sensors total on the truck (1 before the engine and 1 after).
Are you saying that there's actually 2 sensors after the engine (on the exhaust pipe) ?
thanks a lot btw
Pat
gamefreakgc
Elite Member
Newer vehicles have a setup kind of like that (but all O2 sensors are on the exhaust) where one O2 is accessed in the engine bay. However ours are not, both are downstream and accessed under the truck.
The one before the catalytic converter is the one you want, that's the heated sensor. The rear sensor near your muffler is sort of an emissions sniffer, to make sure your exhaust is okie-dokie according to all those federal regulations.
TheDurk
Elite Member
It's not too hard at all, I'm sure you could do it.
Let your 4Runner cool down to be able to touch the exhaust components without burning yourself. Makes this less painful. You're looking for the first sensor on the exhaust pipe coming down from the engine. There's two: one before the catalytic converter and one after. You want the upstream sensor. It'll look something like this:
The sensor itself is secured by two 12 mm nuts. You'll need a deep socket or O2 sensor socket to take it off. I do not recommend using any sort of adjustable wrench or standard wrench since these nuts strip very easy. If it doesn't come off with reasonable force, use a liquid penetrant such as CRC's Freeze Off or Liquid Wrench, you can buy these at your local auto shop.
Once you get the sensor nuts off, the sensor slips right out. There's a old gasket probably stuck to the exhaust pipe, take this off as well. If chunks of it are left behind, lightly scrape it off but don't damage the pipe surface. You want this surface to be as smooth as possible to prevent any exhaust leaks.
You'll have to disconnect the O2 sensor wire from the main wiring harness. Follow the wire up until you find the connector. Disconnect using a pair of pliers or by hand if you can. Just be sure not to damage the receiving end of the connector (the old sensor doesn't matter).
Now just plug in your new one and start tightening back down the nuts. If the old nuts are damaged or rusted out, I recommend getting some new ones. Take them to an auto parts store or hardware store and have them match them. Torque the new ones to 14 lbs/ft. If you don't have a torque wrench, this is just snugged tight so it doesn't come loose. Any tighter and you risk stripping the thread.
WHOAAAA!!!!! P0141 is Bank 1 Sensor 2. That is the post-cat sensor (furthest from the engine). Otherwise, good tips.
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gamefreakgc
Elite Member
Oh my bad, I didn't know the rear one could throw any code other than P0420!
In that case, in reference to your photo it's the last sensor, nearest to the muffler.
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PNW yota
New member
Sorry I'm bringing one back from the dead here. I'll need all your juju for this one...
Started throwing P0420 code for the O2 sensors. After just clearing the code a few times I decided it was time to replace them. Ordered parts and crawled under to find this.
Looks like someone tried this before...
Bolt extractor on the way from amazon. I'll try a wire wheel to clean them up and see if there is any nut left to grab (the left looks completely rounded off). PB blaster, chisels and propane torch for heat will be ready as well.
Cross your fingers for me!
Started throwing P0420 code for the O2 sensors. After just clearing the code a few times I decided it was time to replace them. Ordered parts and crawled under to find this.
Looks like someone tried this before...
Bolt extractor on the way from amazon. I'll try a wire wheel to clean them up and see if there is any nut left to grab (the left looks completely rounded off). PB blaster, chisels and propane torch for heat will be ready as well.
Cross your fingers for me!
Sorry I'm bringing one back from the dead here. I'll need all your juju for this one...
Started throwing P0420 code for the O2 sensors. After just clearing the code a few times I decided it was time to replace them. Ordered parts and crawled under to find this.
Looks like someone tried this before...
Bolt extractor on the way from amazon. I'll try a wire wheel to clean them up and see if there is any nut left to grab (the left looks completely rounded off). PB blaster, chisels and propane torch for heat will be ready as well.
Cross your fingers for me!
yikes, those look bad, are you doing the rear one too ?, depending on the year thats one can need a big special socket, at least it was on my 2000 and is on my 2001. maybe can be done without the special socket, the special one has a cut out in it for the wires to pass through, is one big built in head, like a spark plug has, I think the earlier onew were also the two bolt style front and back. I could be wrong
good luck.
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PNW yota
New member
That is the rear.
PNW yota
New member
I actually have Seafoam deep creep on the shelf but I'll look into the CRC too. Thanks for the tip.
