P0420 2001 4Runner

R

rpearlberg

New member
Just came from an oil change and had them check the codes on my CEL. Suggested two new cat converters for about $1K total, or to try a Induction and Fuel Injection cleaning for about $200. How do I clear the code (I'm sure it'll come back on, but I'd like to clear the lights and see what happens).
 
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You can get an ODBII scantool that can reset codes and use it to read/clear codes yourself. Or, you can take it to an Autozone or Advance Auto and get them to do it for you for free. Or, you can remove the neg battery cable for a few minutes and let everything reset. The code may come back in 20 miles, 200 miles, or more, once the proper drive cycle has been satisfied.

That code comes from the rear O2 sensor. It indicates a faulty CAT system but could very well be the sensor itself. You can find the proper part and order it online for well under $100 and swap it out yourself and see if it fixes the issue. I had the same code in November and swapped the sensor. It is now May and the code has not come back.
 
its not difficult. If you've never done anything to your car in the past, maybe grab a friend to help you. Depending on where you live (saltbelt) your o2 nuts might be rusted on and difficult to remove, so take a look underneath to check it out first.

I used this writeup when I changed mine awhile back. Theres a lot of other helpful writeups on that site, too.

4Runners.org - Changing Your 02 Sensors
 
rpearlberg said:
Thank you!! Any recommendations on where to buy the sensor (you happen to know the model number I need?)
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Read the tutorial and documentation sticky, there is a link there for denso o2 sensor, and it has all the info you need for the part number.

Buy denso only, and buy from Amazon. That is the cheapest you can get them for, and Denso is the best, other brands sometimes throw codes right out of the box.
 
Thanks! I got the new sensors, now I just need to install them! Can I do this in the driveway without lifting the vehicle?
 
Yep. The fronts have two nuts that are probably totally rusted on (going to need new ones) and the rear threads right into the exhaust - similar to a spark plug. For that one, you'll either need an O2 sensor socket or a big wrench. Probably want to hose both sensor connections down with some good penetrating oil (PB Blaster works wonders).

Also, try doing a search for this stuff either here or via Google ("3rd 4runner O2 sensor") and you'll find a plethora of information on how to do this.
 
fish0281 said:
Yep. The fronts have two nuts that are probably totally rusted on (going to need new ones) and the rear threads right into the exhaust - similar to a spark plug. For that one, you'll either need an O2 sensor socket or a big wrench. Probably want to hose both sensor connections down with some good penetrating oil (PB Blaster works wonders).

Also, try doing a search for this stuff either here or via Google ("3rd 4runner O2 sensor") and you'll find a plethora of information on how to do this.
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You sure about that? Mine is in there with two nuts, just like the front one.
 
PitbullRescuer said:
You sure about that? Mine is in there with two nuts, just like the front one.
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+1. Mine is a 2000 Cali model but the rear O2 fits just like the front one - with the 2 studs coming off the pipe that pass through the 2 holes in the sensor. Sounds like 2001 was made different or someone has a modified exhaust system that they didn't realize was modified.

No need to change the front sensor to try and correct that code. It's the rear sensor that throws that code.

You may need to soak the nuts with PB blaster to loosen them up. It also helps to use a 6 sized socket instead of the cheaper style socket.
 
PitbullRescuer said:
You sure about that? Mine is in there with two nuts, just like the front one.
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Yeah, '01-'02 have the screw-in rear plugs. This tip I posted in the other thread should apply here too as to the front sensor:

Tip: Your '01 should be the same as my Cali. '99. No bolt on plug. You need to undo the SENSOR first. Then pass it up and over the pipe and let it fall down the other side. You can then undo the plug easily. Do NOT try to undo the plug first as all the DIY's say to if you have a '99-'00 Cali. or any '01-'02, because it is virtually impossible. The DIY's I have seen are all written for the old single-cat exhaust, not the newer air/fuel dual cat exhausts.
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I'm trying to get a couple of quotes to have these changed out for me. I've already bought the new sensors. Although it sounds like it's not that bad to do, I don't feel too comfortable under the car....

Here is a question from one of the mechanics...
The labor to replace an O2 or A/F sensor would depend on which sensor it was (B1S1, B2S1, etc.). With a little more infrmation we could provide you with an accurate quote. Thank you.

Any help?
 
1) you only have Bank 1 (B1) sensors; Bank 2 would be for a dual exhaust setup.
2) S2 refers to the rear sensor, the one I assume you're trying to replace. S1 is for the front sensor, which is actually a bit different.
3) I'd really encourage you to try this out yourself. It is incredibly easy, you don't need to lift the truck or anything. If you are getting a quote, it should be an hour at most, but it'll probably take them more time to pull the truck in the stall than it will to change the sensor. I'd expect an hour estimate and all sorts of other "suggested" maintenance.
 
There is a service center at the end of my street...he said it would be under an hour (depending on how hard it is to remove the old ones)...
 
fish0281 said:
1) you only have Bank 1 (B1) sensors; Bank 2 would be for a dual exhaust setup.
2) S2 refers to the rear sensor, the one I assume you're trying to replace. S1 is for the front sensor, which is actually a bit different.
3) I'd really encourage you to try this out yourself. It is incredibly easy, you don't need to lift the truck or anything. If you are getting a quote, it should be an hour at most, but it'll probably take them more time to pull the truck in the stall than it will to change the sensor. I'd expect an hour estimate and all sorts of other "suggested" maintenance.
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Seriously, try it yourself. Take it to the shop if you fail, but I doubt you will.

If you don't have rust, it is literally a 5 minute job with nothing more than a crescent wrench.
 
Nelsonmd said:
Seriously, try it yourself. Take it to the shop if you fail, but I doubt you will.

If you don't have rust, it is literally a 5 minute job with nothing more than a crescent wrench.
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...like you would know what working on a truck with no rust is like :)
 
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