P0420 & P0430 codes (1 Viewer)

[BillyBaroo]

Noob apology up front --esp if this is already been addressed. I've looked through the forums but didn't what i'm looking for. OK. So here's the short back story and question (s)

I've recently bought my '04 100 series LC and these two codes came on. (P0420 and P0430. Dealer is willing to throw some money at it to help me get it fixed. The Toyota dealer where it's had most of its work said the previous owner knew about the CAT codes but didn't want to do anything with it as he had just sunk 10K into the brakes, axles, timing belt and more. So, now I've been quoted by them $4500 to replace the CAT and O2 sensors. Another local shop quoted $1800 but with aftermarket parts. questions:
1) I was told that LC's are sensitive to aftermarket CATS. And the engine light may come back on. Does anyone know if this is accurate? And is it still "fixed" even if the light comes on.
2) I've read in a few forums on here that they just found ways to adjust sensors to get light off. As the CAT degrades is it damaging the engine? How urgent is CAT replacement?

Bottom line. I just want to do what is safe, smart and cost efficient

Any and all input is welcome. Let me know if you need more information. Thanks!

 

[97 AZ LC]

Try Youtube videos on P0420. There's a ton of them. It seems that nobody wants to buy cats.

 

[BillyBaroo]

Try Youtube videos on P0420. There's a ton of them. It seems that nobody wants to buy cats.

Cool. Thanks I'll check it out

 

[MJK]

Quick and dirty solution is to put some spark plug anti foulers over the downstream o2 sensors, but this isn't really a long term solution.

The 'right way' to fix it is OEM cats, IMO. Looks like McGeorge has them for $1100/ea. Or, you can take your chances with aftermarket via rockauto.

Side note, if your manifolds are shot, now would be a good time to get some Dough Thorley headers.

To me, this boils down to what your expecations of the truck are.

 

[BillyBaroo]

Quick and dirty solution is to put some spark plug anti foulers over the downstream o2 sensors, but this isn't really a long term solution.

The 'right way' to fix it is OEM cats, IMO. Looks like McGeorge has them for $1100/ea. Or, you can take your chances with aftermarket via rockauto.

Side note, if your manifolds are shot, now would be a good time to get some Dough Thorley headers.

To me, this boils down to what your expecations of the truck are.

Thx. V. helpful. Yeah, expectation-wise. Currently the engine isn't losing any power. My hope is to use it mostly as a daily driver and turn it more into a camping vehicle for my kids with some light off road mud at the Gorge. So, my expectation is I'd like to get the engine light off the 'right way'. Although I thoroughly appreciate the quick and dirty way haha!

 

[2001LC]

OEM or good aftermarket shouldn't be a big factor in DTC's (P0430 & P0420) coming back. OEM CAT's are the best, using more materiel and better heat shielding. Many aftermarkets are smaller and do not even have a heat shields.

CAT can outlast a properly running and operated engine. Highest known mileage 2UZ-fe engine, I know of is 1,000,000 miles Toyota Tundra with a 2UZ-fe VVT engine, it had the original factory CATs.

We must always ask especially when both CATs go bad at same time. What caused this to happen!

Most common causes for CAT to go bad, in normal operated and fueled 2UZ-fe:

1. Something up stream of CATs cause them to go bad.
2. Excessive frequent and prolonged idling. OM warns against this.
3. Flooding washing crud into CATs, clogging them. Should find other signs or by scoping CAT see signs.
4. Impact damaging CAT. Not likely both CAT took a major blow at same time without clear signs under the vehicle.

As you can see 2-4 can just be avoid, or insurance related.

It is number 1, that must be found and corrected first. This must be addressed, before replacing CAT or DTC's will most likely come back. Worst case is the engine over-heated and warped both heads. Coolant may enters into CAT's through cylinder camber combustion. If this the case, it should be loosing coolant. But amount may be very small, which makes detecting very difficult and take time to even notice level drop. Very small leak, makes detecting very difficult. Combust gas test can work well here, but can miss the leak if very minor. Whatever the issue, it needs found and correct first.

I'd be speaking with Dealership, asking what cause both CAT to go bad and at same time.


BTW: I can also be as simple as engine run to cool, due to bad thermostat. Which long term can damage CAT's.

 

[BillyBaroo]

OEM or good aftermarket shouldn't be a big factor in DTC's (P0430 & P0420) coming back. OEM CAT's are the best, using more materiel and better heat shielding. Many aftermarkets are smaller and do not even have a heat shields.

CAT can outlast a properly running and operated engine. Highest known mileage 2UZ-fe engine, I know of is 1,000,000 miles Toyota Tundra with a 2UZ-fe VVT engine, it had the original factory CATs.

We must always ask especially when both CATs go bad at same time. What caused this to happen!

Most common causes for CAT to go bad, in normal operated and fueled 2UZ-fe:

1. Something up stream of CATs cause them to go bad.
2. Excessive frequent and prolonged idling. OM warns against this.
3. Flooding, washing crud into CATs clogging them. Should find other signs or by scoping CAT see signs.
4. Impact damaging CAT. Not likely both CAT took a major blow at same time without clear signs under the vehicle.

As you can see 2-4 can just be avoid, or insurance related.

It is number 1, that must be found and corrected first. This must be addressed, before replacing CAT or DTC's will most likely come back. Worst case is the engine over-heated and warped both heads. Coolant may enters into CAT's through cylinder camber combustion. If this the case, it should be loosing coolant. But amount may be very small, which makes detecting very difficult and take time to even notice level drop. Very small leak, makes detecting very difficult. Combust gas test can work well here, but can miss the leak if very minor. Whatever the issue, it needs found and correct first.

I'd be speaking with Dealership, asking what cause both CAT to go bad and at same time.


BTW: I can also be as simple as engine run to cool, due to bad thermostat. Which long term can damage CAT's.

Wow! Amazing info—thx. I’m gonna re-read and distill a bit more. But I get the gist of finding out the root of the issue. Appreciate the input. I’ll post back here as I figure out the next course of action for us—

 

[MJK]

I agree on root cause, and @2001LC knows these trucks better than I do. But, my experience regarding cat longevity has been less favorable than his.

For what its worth, I put 170k on a 3UZ GS before getting the same symptoms. It would throw those same codes in in town driving, but if you took it on a 100+ road trip it would clear up for a while. That is classic behavior for cats on the way out. If you just let it ride, they'll eventually plug up. No Bueno.

Cats can fail for a variety of reasons, and while I agree they CAN last for a million miles, that doesn't mean they always do. Best case scenario for cats is sustained high temp running with proper mix. A set of cats with 200k highway miles are probably in better shape than 100k of city daily driving. That said, 300k and 17 years is a pretty good run in my book.

To me the solution depends on how long you plan to keep it. Just need to get through inspection this year? You have a couple quick & dirty options. Want a few more years? Aftermarket might be the ticket. If its a keeper, OEM all the way in my book. You'll pay more for them but they'll last longer (cheaper generally means less expensive catalyzing materials used).

In terms of likely contributors and/or protecting my investment: I'd check manifolds for cracks, replace 02 sensors and maybe yank/clean the injectors. If the shop just recommended cats and 02, presumably that means no exhaust leaks and no reason to suspect poorly atomizing injectors? Just a guess, I'd check them anyways.

But, as I said, experiences vary. Those are only mine.

 

[2001LC]

I agree on root cause, and @2001LC knows these trucks better than I do. But, in my experience regarding cat longevity has been less favorable than his.

Cats can fail for a variety of reasons, and while I agree they CAN last for a million miles, that doesn't mean they always do. Best case scenario for cats is sustained high temp running with proper mix. A set of cats with 200k highway miles are probably in better shape than 100k of city daily driving. That said, 300k and 17 years is a pretty good run in my book.

I say we're very much in agreement on the key to health CAT(s). "Best case scenario for cats is sustained high temp running with proper mix."


In PO case we've both P0430 & P0420 at same time. This tends to limit causes of failure. It's job of mechanic to look for WHY.

 

[Gator595]

I have the same problem on the passenger side. Is there any other 4.7 that has the same CAT like Tundra or Sequoia?

 

[2001LC]

I have the same problem on the passenger side. Is there any other 4.7 that has the same CAT like Tundra or Sequoia?

Good question! I'm thinking no but I've not looked into it. I do know the 4 runner 4.7L VVT different, and relatively sure GX470 different. The fact all the 4.7l VVT long blocks are the same, But we must swap most all other parts, when using other than 100 series engine. Parts diagram or picture hunt, would be revealing.

If your asking, so you can broaden search for used CAT. Keep in mind it is illegal to sell or install used CATs unless certified (which no one does). EPA fine of $20K. This why no salvage yard will have listed in the USA.

Did or do you have any other codes?

 

[Gator595]

Good question! I'm thinking no but I've not looked into it. I do know the 4 runner 4.7L VVT different, and relitively sure GX470 different. The fact all the 4.7l VVT long blocks are the same, But we must swap most all other parts, when using other than 100 series engine. Parts diagram or picture hunt, would be relieving.

If your asking, so you can broaden search for used CAT. Keep in mind it is illegal to sell or install used CATs unless certified (which no one does). EPA fine of $20K. This why no salvage yard will have listed in the USA.

Did or do you have any other codes?

Nope just the P0430

 

[Gator595]

Nope just the P0430

And the previous owner put a spacer on the down stream O2 sensor. The code came and went for a couple of months and then stayed. If I clear the codes it comes back with in 10 miles. Does this sound like text book bad cat?

 

[2001LC]

With bad CAT I do find code comes back very fast, after short HWY run. But looking at how A/F and O2 are performing, is one of the first steps.

Keep in mind. CATs do not just go bad. It is most always (99 out of 100) something up stream (which can included prolonged idling), impact to CAT or even clogging causing them to fail.

These spark plug extenders are to trick the system. They do nothing to address the problem.

 

[Gator595]

With bad CAT I do find code comes back very fast, after short HWY run. But looking at how A/F and O2 are performing, is one of the first steps.

Keep in mind. CATs do not just go bad. It is most always (99 out of 100) something up stream (which can included prolonged idling), impact to CAT or even clogging causing them to fail.

These spark plug extenders are to trick the system. They do nothing to address the problem.

I know the extender is not a fix I only mentioned it as evidence that this has been going on for a while. I'll check the performance.

 

[Muskyfever]

I had one of those error codes (P0430)for the right cat. I changed both O2 sensors on that side and it went away. I cleaned the MAF also and ran a few tanks of high octane fuel thru it. I’d start with the O2 sensors. The CATs probably aren’t bad.

 

[landarcht]

Gator, I have the same P0430 code for couple of years now, it wasn't until early this year that it would come back up the same day I clear it. Car drives fine and smooth, idle s fine, no loss of power, and engine sounds fine. I cleaned MAF sensor recently it went away for a day and came back. Based on 2001LC's recommendation, I'm going to check if there's vacuum leak next. Car recently had it's 170K service, I had O2 sensors checked, they said no issue, not sure how they checked it? Visual check?
I've tried fuel system cleaners but non worked.
Have you fixed your's yet?

 

[jerryb]

don't lump all 100s into one group of 420 and 30 codes. The vvti compared to the rest will behave very differently.
Even if you're just going to compare the rear narrow band sensors- not one of us knows the ecu effect after the fact..
The reporting from the rear sensors is very narrow. It's affect is greater than I would have thought.
Everyone should have all 4 sensors newer than 5-7 years, narrow or wideband. They're cheaper than coil packs anyway.
Work from the sensor bungs forward and up to the top of the intake. All the posted advice works.
read a book or block off a saturday and watch utube videos.

fix all your exhaust leaks, fix your intake leak, replace the coolant and ambient air sensors and MAF. Inspect your coil packs and change your plugs. Insure your throttle plate opens all the way, clean it. Replace pcv and both hoses. Check unmetered air getting by.
basic stuff.