P0420 wont leave me alone..

[Apounder]

I recently purchased an 05 GX470 and after putting about 600 miles on it or so, the code popped! Well just for s***s and gigs I ran some 44k through it and cleared the code hoping it might help clear it out... Long story short the code is coming on more and more often about every 50k miles if I clear. Little confused on the issue, so do I really need to spend ~900 on a new manifold with cat? Is there any other options or possibilities that could cause a p0420? Is there a dummy plug I could run to not throw a code? Other than that code popping up it runs like a new car...

Thanks for any suggestions!
-Andrew

 

[GXO]

That can be an o2 sensor. Bank 1 is passenger side

 

[GXO]

Bank 1 sensor 1 is passenger front. 2 is rear. Need the detail of the code

 

[Apounder]

Bank 1 sensor 1 is passenger front. 2 is rear. Need the detail of the code

Says threshold 1 so sensor 1?

 

[Apounder]

Oh code reads cat efficiency below threshold bank 1

 

[BlueCruiser84]

You can use a scanner and see what the o2 sensors are doing. Google what to look for. I can't remember.

If the sensors haven't been replaced it might be a good time to do it anyway. It's usually the rear sensor if it's not the cat.

I too got the code on a new to me GX. Two new pre o2 sensors. Old post o2 sensors. Filled her all the way up and added two bottles of Techron and it hasn't come back. Going to the beach next week which should be about 600 miles of highway driving. We'll see what happens.

 

[kbahus]

Bank 1 is actually the driver side on the 2UZ.

Here is what you need to "fix" the P0420 code (if it comes back): https://www.amazon.com/Universal-Sensor-Spacer-Adapter-Isolator/dp/B00OXWZ0VU/?tag=ihco-20

Picture installed on my truck:

 

[co4wheel]

Why does a spacer help.

 

[kbahus]

It causes the post cat 02 sensors to read differently, sort of tricks them. Doesn't work in all cases but does more times than not.

 

[BlueCruiser84]

Link to an explanation of why it works??? That's interesting.

Does it fix the problem or is it more of a bandaid to a cat that is on the way out?

 

[BlackCat]

Link to an explanation of why it works??? That's interesting.

Does it fix the problem or is it more of a bandaid to a cat that is on the way out?

The spacer slows the response of the sensor, tricking the car into thinking the cat is working more efficiently.

 

[kbahus]

It is a bandaid, the only thing it fixes is the check engine light. If you have to pass emissions testing the cats may still need to be replaced. Do you have to worry about emissions testing?

 

[BlueCruiser84]

No emissions for me. I was just curious if it was fixing an issue or masking one. If my light comes back I'll add the spacer. Seems cheap enough and easily reversible!

 

[BlackCat]

It is a bandaid, the only thing it fixes is the check engine light. If you have to pass emissions testing the cats may still need to be replaced. Do you have to worry about emissions testing?

If a spacer actually works and keeps the light off it will then pass emissions in most states that are just looking for OBD codes. Not sure it would work if you live in a state that uses a sniffer, but I would imagine it would.

 

[Bossman]

So, in this case, you would install the spacer on bank 1 sensor 2?

 

[HiLex]

I live in Colorado just recently passed visual and dyno smog inspection with spacers installed in both rear O2 sensors

 

[BlackCat]

So, in this case, you would install the spacer on bank 1 sensor 2?

Yup. A $5 spacer beats a $900 or whatever manifold.

 

[Apounder]

Bank 1 is actually the driver side on the 2UZ.

Here is what you need to "fix" the P0420 code (if it comes back): https://www.amazon.com/Universal-Sensor-Spacer-Adapter-Isolator/dp/B00OXWZ0VU/?tag=ihco-20

Picture installed on my truck:
View attachment 1314823

Going to give it a shot! ordered! Thanks

 

[tacoduck]

subbed for outcome. I have a downstream o2 sensor giving me grief.

 

[GXer04]

I'm chasing this same code on my 04. I've had the truck a couple months, and recently discovered an exhaust leak at the joint between the cat and cross pipe. This is just before the O2 sensor and my understanding of O2 sensors tells me the leak would throw the code. I replaced the gasket which kept the code away for a week, but the leak and code returned. I ordered another $2 gasket as inspection revealed it's bad again. I'm thinking I damaged it on installation.

You can check for the leak on cold start up with your hand.