2001 4Runner oxygen sensor mystery

[Southernbike]

I replaced the rear converter on my 2001 4Runner with a Magnaflow Part # 49579 converter and ordered a OEM Toyota rear oxygen sensor (89465-35580) at the same time. The opening for the O2 sensor on the converter is a oval shaped bolt on plate. The OEM Toyota sensor is a round screw in sensor. When you look at the sensor on any Toyota parts site it shows the oval plate attached to the sensor, but the one I have does not have it. Toyota said this is the correct part and they have no idea about the plate, but they even show a gasket that goes under the plate. Magnaflow said this is the correct part for my 4Runner.
Any ideas?

 

[kball]

Check your sensor part number against the chart on this site.

Oxygen / AFR Sensors - Underdog Racing Development

 

[gamefreakgc]

Looks like to me you have the front O2 sensor, but you need the rear. In my understanding all the front sensors have flanges on them like you ordered, but the rear ones are all screw-in with no flange.

 

[sprdav33]

Gamefreakgc is correct, you have the wrong sensor. I replaced both on my 2001 and remember both styles of 02 sensor. Just don't remember which one was front and back.

 

[Southernbike]

Check your sensor part number against the chart on this site.

Oxygen / AFR Sensors - Underdog Racing Development

These are aftermarket, but I did see that the 99-00 rear sensor is different from the 01-02 rear sensor. I wonder if the Magnaflow direct fit convertor is not a direct fit for the 01-02?

 

[Southernbike]

Looks like to me you have the front O2 sensor, but you need the rear. In my understanding all the front sensors have flanges on them like you ordered, but the rear ones are all screw-in with no flange.

The OEM Toyota one I ordered is the screw in sensor in the right side picture, the sensor in the left side picture was to show what my magnaflow converter needed as the converter is already installed, I should have been more clear on the pictures.
The confusing thing is that Toyota shows a image of the flange sensor in the parts break down for the rear sensor and they also list a flange gasket and two nuts for the rear sensor.

 

[19963.4lsr5]

You can buy a adapter plate the 97 had a screw in sensor threaded into a plate and plate bolted to cat for my front sensor on the puppy hauler


Sent from my iPhone using Tapatalk

 

[TheDurk]

The OEM Toyota one I ordered is the screw in sensor in the right side picture, the sensor in the left side picture was to show what my magnaflow converter needed as the converter is already installed, I should have been more clear on the pictures.
The confusing thing is that Toyota shows a image of the flange sensor in the parts break down for the rear sensor and they also list a flange gasket and two nuts for the rear sensor.

I suspect you were looking at the wrong EPD. The system holds both Cali. spec and standard exhaust info for 2001, even though all '01-'02 4Runners were Cali. spec. regardless of where they were sold. The standard shows the flange, and a single cat. The Cali. EPD doesn't really show the bunghole clearly, but it's not a flange, and has two cats.

The Magnaflow was probably designed to fit '99-'02 Cali spec 4Runners, but was equipped with the flange rear sensor like the '99-'00 Cali trucks. Electrically, it should not make any difference, so just get what fits. Both Cali and standard use a standard O2 in the rear, just the mount style changed in '01-'02 on the Calis, which was the only one that existed in North America.

Hope this made sense. It gets confusing.

 

[Southernbike]

I have called myself searching for an adaptor plate, I have found a few, but none with threads for the O2 sensor to screw into. Do you know anyone that has one with threads for the O2 sensor?

 

[TheDurk]

I have called myself searching for an adaptor plate, I have found a few, but none with threads for the O2 sensor to screw into. Do you know anyone that has one with threads for the O2 sensor?

No, and I doubt it's possible to make one. The flange bunghole has to be smaller (it's very tight) than the thread on those screw-in sensors (which are pretty big), so any such adapter would have its threads above the flange, and that would have the business end of the sensor too far out of the gas stream to function. Or you would have to drill out the bunghole, and I strongly doubt if there is enough material to do that given you would need to insert a thread sleeve around the sensor thread itself. I'm guessing non-starter on the adapter idea. Just get a flange sensor.

 

[Southernbike]

I called Magnaflow back and got a guy who was very helpful, you are right, these are designed for the earlier model Cali 4Runners. He said they were aware of the problem but could not find and 01-02 4Runners to test. He did say that this might work
https://www.summitracing.com/parts/smp-sgf1/overview/make/toyota/model/4runner
He said it might as he had never used it, I just wish they had put this in the fitment notes as my truck is now down.
Do you think a rear O2 sensor from a 99-00 4Runner would work? My dealer said they have the flange mount, bout could not tell me if it would work. The plug looks the same.

 

[TheDurk]

I called Magnaflow back and got a guy who was very helpful, you are right, these are designed for the earlier model Cali 4Runners. He said they were aware of the problem but could not find and 01-02 4Runners to test. He did say that this might work
https://www.summitracing.com/parts/smp-sgf1/overview/make/toyota/model/4runner
He said it might as he had never used it, I just wish they had put this in the fitment notes as my truck is now down.
Do you think a rear O2 sensor from a 99-00 4Runner would work? My dealer said they have the flange mount, bout could not tell me if it would work. The plug looks the same.

I don't think that flange will help, as it has no threads. It is for building a system from scratch that uses the flange. The answer indeed is to use a flange type from '99-'00.

https://www.densoproducts.com/product.aspx?zpid=18115

https://www.densoproducts.com/product.aspx?zpid=18213

You can see the plugs and specs are the same. The wire length looks like it might be longer on the '99-'00, although that should not be an issue. Just ziptie it if you have to. I can't absolutely guarantee it will work, but it's what I would do in your case. Worst case you can always install a URD Sim if it sets a P0420 code. With a Magnaflow or any after market cat, you will probably end up there anyway.

I use those links because the pics are better than Amazon, although I would buy wherever you get the best deal on that Denso p/n.

I have never seen an explanation of WHY Toyota went with the threads on those rear '01-'02 sensors. I would love to know.

 

[Southernbike]

I don't think that flange will help, as it has no threads. It is for building a system from scratch that uses the flange. The answer indeed is to use a flange type from '99-'00.

https://www.densoproducts.com/product.aspx?zpid=18115

https://www.densoproducts.com/product.aspx?zpid=18213

You can see the plugs and specs are the same. The wire length looks like it might be longer on the '99-'00, although that should not be an issue. Just ziptie it if you have to. I can't absolutely guarantee it will work, but it's what I would do in your case. Worst case you can always install a URD Sim if it sets a P0420 code. With a Magnaflow or any after market cat, you will probably end up there anyway.

I use those links because the pics are better than Amazon, although I would buy wherever you get the best deal on that Denso p/n.

I have never seen an explanation of WHY Toyota went with the threads on those rear '01-'02 sensors. I would love to know.

Thanks! You have really helped me out! Looks like the 99-00 sensor is the way to go. I just wish that Magnaflow would have included an adaptor with this cat. It would be cheaper than making another model I would think.

 

[01thunder]

as said previously, get the one with the flange and correct connector. aftermarket companies don't always make stuff every car/truck. you have to adapt stuff sometimes.

 

[01thunder]

I replaced the rear converter on my 2001 4Runner with a Magnaflow Part # 49579 converter and ordered a OEM Toyota rear oxygen sensor (89465-35580) at the same time. The opening for the O2 sensor on the converter is a oval shaped bolt on plate. The OEM Toyota sensor is a round screw in sensor. When you look at the sensor on any Toyota parts site it shows the oval plate attached to the sensor, but the one I have does not have it. Toyota said this is the correct part and they have no idea about the plate, but they even show a gasket that goes under the plate. Magnaflow said this is the correct part for my 4Runner.
Any ideas?

it looks like the first one unscrews from that flange.

 

[Southernbike]

Just a follow-up on this-
I purchased the Denso O2 sensor that kball suggested to try. This one was made for the 99-00 models and worked with the Magnaflow flange opening. No problems at all, runs great and no codes.
I also found this
SGF1 Oxygen Sensor Mounting Flange Bracket With Gasket (44mm) for Toyota Lexus
SGF1 Oxygen Sensor Mounting Flange Bracket With Gasket (44mm) for Toyota Lexus | eBay
that would have let me use the correct sensor for my 01 4Runner.
This was part of a project that involved replacing both cats with the Magnaflow cats and the muffler with the Gibson stainless steel unit.
Thanks to all that gave advice and helped with this!