memokc

Replaced ALL parts with OEM Denso PARTS: plugs, both A/F sensors, rear O2 sensors, had exhaust looked at a well respected shop, no leaks, I use Teir 1 91 octane gas, replace gas cap OEM and I still get an F-ing P0420 code and it is the only freaking code!! I bought this truck from my boss & it was his wife's who only had it serviced at Lexus & I have ALL service receipts. I looked through every receipt & only once was there ever a report of the check engine VSC etc lights on and it was fixed with a speed sensor if I recall. Which f-ing CAT is needed to be replaced with obviously an OEM. I swear this thing is MINT condition with only 112K on it. I got a great deal on it but wish I would have never bought it, my 04 Escalade with 150K (NO CODES!!!) on it has NEVER had problems like this piece! This thing does run like a freaking bat out of hell, I will give it that but the F-ing lights and the damn P0420 code make me want to sell it but I have had to replace some secondary emission pump on it at like $2K so I am loosing money on this as it is. Just want to get the damn CAT changed to fix it properly and then I might just sell the damn think. If you live in OKC, let me know if interested in buying it. Sorry so long of a message just f-ing pissed off!!!!

chiph9

The bad part of this code is it doesn't tell you which cat is having problems.

Take it to a different mechanic, have them rap on the cat housing to see if there are any loose chunks in there. And then take it off and look through it to see if the element is clogged.

Also look for broken/bad/melted wires going to the O2 sensors. And that the heater line has 12v on it (pretty sure the 4.7 uses a heated O2 sensor...)

Chip H.

memokc

I can double check the O2's but they are brand new. Thanks Chip!

memokc

Anyone heard of an ECM reflash for our model of SUV's? I have heard the thresholds are so dang high that is why so many get P0420 codes and if there is a reflash it can lower the percentage thus eliminating the P0420 code all together? Just thought I would ask.

mswtoyota

I have not heard about a reflash, but I have used spark plug non-foulers inline with the rear O2 sensors on a Chevy trailblazer to get a similar code to go away. It may provide a cheaper temporary fix since the upstream cats start around $300 on Rockauto.

memokc

Thanks for the info, if those would work I would be happy, anyone have success on our Lexus? My SUV runs awesome I am just tired of the lights every so often! Other than that I love my SUV.

FrankT

I have used; or should I say, am using those spacers to completely eliminate my p0420 code in our GS300.
I used 2 spacers per sensor.
One spacer needs to be drilled.

This is one of many many threads on the net. And the source of the pic... https://www.tacomaworld.com/threads/...e-0420.210106/

memokc

I see these for sale already made on eBay, why wouldn't I buy one already made at a 90 degree angle, are they not the same thing and solving the same problem?

LexRex

Will these fit with the type of O2 sensor fitting we have on our trucks? Don't we have a 2-bolt flange?

Better look under your truck before you order.

mswtoyota

My 2006 GX has 4 screw in O2 sensors, but I have no idea of the thread pitch or size, and if there is room for the spark plug non-foulers.

Another user here, Odissey states: "And I forgot to another element tuning
This is it: URD Rear O2 Simulator
Had to install more than 4 years ago and since then I have the problem " VSC + VSC OFF + CHECK ENGINE" forgotten"
Possibly another option for $150.

memokc

that looks pretty complicated to hook up but I am sure I could figure it out. I really don't care about emissions and I am not trying to side step them, we don't have emissions in Oklahoma so I am not worried them.

memokc

read more about it, how does it install, I don't know if I want to rig something that elaborate into my stock ride. What all does that intail to hook up? There is another muffler shop in town that is supposed to be top notch that specializes in Cats that I am going to go to have him look at first to see. He has great reviews for being completely honest, so I am gonna give him a chance to look it over for me first. I might just bite the bullet & have new cats installed?? The truck runs like Awesome so I don't know, just hate when then the damn lights come on periodically! Thank you for all the responses!

mann777

Yes the options has got the Re-flashing option via the Tech stream tool. And GX had issued and resolved via a TSB.

memokc

man777, can you tell me more about this? I have a $300 scan tool but it's not a tech stream tool? Where can I go to get mine reflashed?

mswtoyota

Complicated? No. It simply plugs inline between the factory harness and the O2 sensor. No cutting, no splicing, and you can return it to stock at any time. If you can replace an O2 sensor, you can install the O2 simulator in half the time. I guess it comes down to if you want to buy new cats $$$, or the O2 sim $.