P0420 and P0430 - 2006 LC (2 Viewers)

[2001LC]

Great thanks for the up date. O2's (rear O2's) have had the most success again!

Keep the reports coming from those P0430 & P0420 codes

 

[white_lx]

An exhaust leak can also trigger these codes. Even when the leak is downstream (!) of the sensors. Always good to check for a leak first.

 

[2001LC]

I know exhaust up stream can. This is first I've heard of down stream. How far down stream are you talking?

 

[white_lx]

I know exhaust stream up stream can. This is first I've heard of down stream. How far down stream are you talking?

I've seen these codes occur with a leak about 10-12" downstream. They seem to happen when the TRAC system activates in snowy conditions. I think it has to do with the sudden drop in throttle causing strange acoustics in the exhaust maybe temporarily causing a reverse flow? After a while they will then automatically clear.

 

[2001LC]

An exhaust leak can also trigger these codes. Even when the leak is downstream (!) of the sensors. Always good to check for a leak first.

I've seen these codes occur with a leak about 10-12" downstream. They seem to happen when the TRAC system activates in snowy conditions. I think it has to do with the sudden drop in throttle causing strange acoustics in the exhaust maybe temporarily causing a reverse flow? After a while they will then automatically clear.

Thank you for the reply.
Edited: What year did you see this on?

So was the leak at the gasket or a hole in the pipe before or after that first joint?

I sure like to see comments from a few other on issue of post exhaust leak?

@Julian Stead perhaps you've something to add here?

 

[2001LC]

@duggy perhaps you've something to add here on post CAT exhaust leak & P0430 & 420?

 

[duggy]

@duggy perhaps you've something to add here on post CAT exhaust leak & P00430 & 420?

I haven't seen any cars with issues pertaining to these codes with exhaust leaks, but these 2 codes pop up on 1UZ based engines often. I usually replace the up and downstream O2 sensors and monitor for any codes coming back up. I'm 3/3 so far, 2 100 series, and 1 GX470.

 

[2001LC]

I haven't seen any cars with issues pertaining to these codes with exhaust leaks, but these 2 codes pop up on 1UZ based engines often. I usually replace the up and downstream O2 sensors and monitor for any codes coming back up. I'm 3/3 so far, 2 100 series, and 1 GX470.

Thanks @duggy

I've seen a couple of 98-05 non VVT with bracket ripped out of exhaust crossover Y pipe, leaving a large hole. They did not throw a code.

I've seen large holes in mufflers again in non VVT, again not throw any code.

The VVt seems to throw more of these codes. Perhaps they're more finally tune or sensitive to variation. But still trying to see how a post CAT exhaust leak could cause this.

I see where the FSM states as/in system tree checks "Exhaust system leaks". I did not see where in specific pre or post.

I've given advise on a 06LC w/200K to replace O2's (rears) now. He has noted and exhaust leak post CAT, which I'm waiting on pictures of. I hope he does O2's first. If no more codes afterwards, we 'll have a good handle on issue. If codes reappears then exhaust would be next. I just hope he does not do both at same time or will never know, which if either correct issue.

 

[white_lx]

Thank you for the reply.
Edited: What year did you see this on?
So was the leak at the gasket or a hole in the pipe before or after that first joint?

This was on a '02 LS430 (3UZ-FE) at the first gasket after the oxygen sensor. I had already bought the sensor, but the problem went away as soon as the gasket was replaced. Code would occur only when the traction control was activated.

 

[rroverbkk]

I had these codes on an 01LX many moons ago.

Changed the rear O2 sensors and it was good as new.

 

[looking4lc]

I had these codes on an 01LX many moons ago.

Changed the rear O2 sensors and it was good as new.

Me Too

 

[SICARIO]

I may be installing the downstream sensors on my 03 lx470. A few of the nuts are corroded beyond use. Does anyone know the size of the nut so I can replace them with stainless versions?

Thanks,

 

[SICARIO]

I just ordered O2 sensors. My obd2 reader said the issue was with bank 1. Do these voltage readings reflect that?

 

[Jae]

I just ordered O2 sensors. My obd2 reader said the issue was with bank 1. Do these voltage readings reflect that?

View attachment 1644098

SICARIO: Is your truck having P0420 code? B1S2 should have flat voltage as like B2S2. The issue could come from bad downstream O2 sensor. In order to check it, you can install PS's O2 sensor to DS's one. If it still shows the P0420, the issue would be DS catalytic converter or some leak on DS' exhaust pipe. I'm having the similar issue(P0430), PS catalytic converter efficiency. I swapped downstream O2 sensors, but still having the same P0430 code. I tried to check any leak on exhaust pipe, but it is difficult to find any leak. So, I am planning to swap catalytic converters between PS and DS to confirm the issue from PS catalytic converter.

 

[SICARIO]

SICARIO: Is your truck having P0420 code? B1S2 should have flat voltage as like B2S2. The issue could come from bad downstream O2 sensor. In order to check it, you can install PS's O2 sensor to DS's one. If it still shows the P0420, the issue would be DS catalytic converter or some leak on DS' exhaust pipe. I'm having the similar issue(P0430), PS catalytic converter efficiency. I swapped downstream O2 sensors, but still having the same P0430 code. I tried to check any leak on exhaust pipe, but it is difficult to find any leak. So, I am planning to swap catalytic converters between PS and DS to confirm the issue from PS catalytic converter.

It is the P0420 code. I believe I had a 430 as well, but I haven't seen that come back in a few weeks.

 

[RECRUISER]

My p0420 and p0430 came back on permanently. So I have changed both cats with Magnaflow direct fit HM grade, item # 93142.
So far, problem solved.
This is the price for BOTH. Then my local shop put them on for me.

 

[RECRUISER]

So two weeks after installing the new cats (see above ebay photo) there have been NO check engine lights. For a total of $800 ($275 apiece for the direct fit cats and 150 labor) my problem is fixed.
If you go this route, make sure that you fix any "Upstream" problems first or they will eventually overwhelm your new cats again. For me this was a overlooked and clogged PCV valve and what looked to be the original spark plugs (200,000 miles on them probably), new air filter.

 

[2001LC]

So two weeks after installing the new cats (see above ebay photo) there have been NO check engine lights. For a total of $800 ($275 apiece for the direct fit cats and 150 labor) my problem is fixed.
If you go this route, make sure that you fix any "Upstream" problems first or they will eventually overwhelm your new cats again. For me this was a overlooked and clogged PCV valve and what looked to be the original spark plugs (200,000 miles on them probably), new air filter.

Did you replace any of the O2's?

 

[RECRUISER]

I had both 420 & 430 codes so I replaced both sensors on the driver's side (bank 1), they all looked like they had already been replaced by the PO, but regardless I did it anyway and, no change. The 02 sensor route should always be tried first (at least on one side) to see if any change occurs.
It is an awesome vehicle and for $800.00 I went for the jugular of repairs and got it done right!
I was also afraid of fuel trim which the engine changes to compensate for the P420 & P430 lights being on. Enough fuel trim over enough time can ruin your engine via wall wash, & melted pistons etc... caused by too much fuel.

 

[RECRUISER]

Just a final follow-up 3 months after my replacement cats were installed. I have not had ANY reoccurrence of my codes since installing the direct fit catalytic converters that I found on eBay. Problem is completely solved after 3 months of trouble free driving.