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Fault Codes P0430 And P0420 On Ls430


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I removed the heat shields to weld up the holes and never put them back on. Perhaps not ideal but I didn't feel like spending $1,200 for a new Y pipe just so I could put shields back on. Once an after market Y pipe is available for my year (2004) then maybe I'll swap it out. I believe you can buy one on ebay for <$300.00. Might be a cleaner solution. Also I think this is Stainless steel so should last longer than the plain steel OEM pipe...

http://www.ebay.com/itm/2001-2002-2003-LEXUS-LS430-CATALYTIC-CONVERTER-51868-/250752773519?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3ALexus|Model%3ALS430&hash=item3a6207ad8f&vxp=mtr

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In post #22, you can see the stainless steel worm-drive type clamps that I used to reattached the heat shields. Purchased from the local Ace hardware store. They are not all that large, maybe 2 1/2 inch diameter. I really do not see the shields as being all that important but since Lexus went to the trouble of installing them, I decided to put them back on. Probably a fire-prevention issue for all of those off-road excursions that we so often take with the LS. :whistles:

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  • 3 weeks later...

While on the subject of P0420/430 I thought it may help someone in the future to recount some of my recent experience.

I had a horrible power loss problem that was getting progressively worse and I was getting these P0420 and/or 430 codes coming up.

It turned out to be failed aftermarket MAF sensor (which I had put on in trying to diagnose a mis-fire); for some reason no MAF sensor codes were showing up.

I put back the ancient Lexus MAF and order was instantly restored. Probably unusual but it did happen so might help someone down the line.

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  • 2 weeks later...

I have a 2001 LS 430 with the P04030 Code. I am taking it in to have the heat shield removed to look for cracks in the Y pipe. I hope it is the root cause of my code. I hate to purchase a new Cat or O2 Sensor and have the CEL light still on. Wish me luck

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It may not be much of a crack so don't expect to find a large one. Once the shield are off you can listen for it with a 2-3' length of flexible tubing. Hold one end near your ear (don't stick it in your ear!) and move the other around the suspected leak. Once you pass tube over the leak you will hear it!

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Today I found a crack in my exhast pipe!

With the heat shield removed I found a hairline crack that was on the top of the exhaust pipe about 6 inches downstream from my O2 sensor.

I had to use a mirror to get a good photo of this. Look to the left of the sharpie line on the exhaust.

Thanks for sharing your experience it has saved me $$!

post-92346-0-10915500-1334941574_thumb.j

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  • 1 year later...

Hello boblexus430,

I have the exactly same problem on my 2003 LS430. There was a leak on the passenger side behide the O2 sensor just inside the heat shield. I took it to local repair shop. They cut out the leaking section and welded a new pipe for the area. It cost only $80. But the heat shield was taking off. Anyway, it's a quick fix for the leaking and noise.

I had the same problem and got it resolved by having my muffler shop welding two new pieces of straight pipe for $150...I have driven over 500 miles and the codes have not reappeared!!

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  • 2 weeks later...

hey guys,

2006 lexus gs430 (90,000mi~)

IF my issue was a bad Catalytic converter(s) / leak(s) in exhaust / bad O2 sensor(s) - which one of these is most likely to be ruled out since the CEL didn't come back (after clearing via ODB) until over an hour of driving / city and highway...

or was this delay just because the cars computer data was erassed and it took that long to log enough data to make the judgement that something if off and set off the check engine light + Yellow indicator with exclamation mark also on (Brake System Warning Light (yellow) and the TRAC light is also on (suggesting that traction is OFF)

your help / suggestions are appreciated.

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  • 5 months later...

I just bought my 2006 GS 430. Beautiful car. it has the error codes noted in this post and an audible exhaust leak under the drivers seat area... Dealer says new cats needed, he would be happy to do this for $3500.00!! this thread will hopefully have just saved me a ton of money! I will update once I get repair done. Thank you to everyone for sharing your successes.

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Awesome. Take it to a local muffler shop and have them weld in the cracks and or add some patches. Probably under $150 all in.

Makes you think twice about dealers motives when they prescribe all sorts of unneeded parts.

Either that or buy something like this and bolt it in....

http://www.ebay.com/itm/2001-2002-2003-2004-2005-2006-Lexus-LS430-4-3L-Front-Y-Pipe-with-Catalytic-OBDII-/281370791321?pt=Motors_Car_Truck_Parts_Accessories&hash=item4183018d99&vxp=mtr

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Thank you for the quick response to my comment, especially since you were the main contributor to this thread.

I know your information has saved may people thousands of dollars. I am hoping that I will be one of them.

This morning I removed the stainless heat shields on both sides of the Y pipe and exposed the leaks, just EXACTLY like the pictures from earlier in this thread.

I didn't even mess with trying to get those rusty bolts out of those rusty clamps. I just grabbed the bolts with a big pair of electricians plyers and bent the bolt mountings back and forth, back and forth about 20 times and the clamps snapped right off. About a 5 minute job. I knew I wouldn't used those clamps again so I didn't waste my time on them.

After I got the shields off and the old insulation around them, I called my local muffler shop (as you have just suggested) and asked if he could repair it, and he said what kind of vehicle is it on?

When I told him a 2006 LEXUS GS 430, he was familiar that this was a common problem with them and asked me " why don't you just let me cut out the 2 bad sections and then let me weld in new pipe, and I don't even have to take the pipes off the vehicle."

I asked him how much that would cost and he said $40 per side!!! OK, I agreed before he had a chance to think about it and raise the price.

I am taking it to him tomorrow morning 9/30/2014 at 10:00 am and should have it back by lunchtime.

So AT THE LEAST by this time tommorrow, I will no longer have an exhaust leak and if I'm fortunate, I will have spent a grand total of $80, and I will be minus an annoying CEL on the dash.

I will post in a few days (allow the codes to hopefully clear) and let you know.

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I'm confident you'll be resolved. When I did the before and after (welding) the OBDII scans of the secondary O2 sensor it was unmistakable.

I'm 30,551miles (1072 days) since the fix with no issues!

If you have an OBDII scanner you can reset the code right away. You can also disconnect the battery for a few minutes if you don't have one. The secondary CAT code is one that is monitored for a few hours of run time after it is reset so you need to log a few miles before you can be sure it doesn't return.

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OK this post is for posterity.

I just saved at least $3000.00 today I believe. As of now I no longer have the CEL error codes, and no longer have CHECK VSC flashing, nor do I any longer have the Traction Control yellow light lit. So that's 4 error codes that were cleared by this simple and inexpensive repair.

I have driven for 2 hours today and no return of any of the above error codes all related to the Catalytic Converters and O2 sensors.

I don't know if this is a permanent fix like CuriousB experienced (But as of today a real change in my vehicle status has occured) as previously all lights would reappear within about 30 minutes.

REVIEW OF SYMPTOMS:

I had an exhaust leak on both sides of the Y Pipe just behind the O2 Sensors that I could hear from underneath the vehicle along with all the CEL's listed above (4 in all including P0420 and P0430).

SOLUTION:

Took vehicle (GS 430 2006) to local muffler pipe this morning (September 2014) They put it up on the rack and cut the two spots that were leaking out and welded in new pipe. Total time for repair 45 minutes.

Estimate was $80 when I made appointment. When they were done they said that it was less work than they thought and FINAL BILL FOR REPAIR WAS ONLY $50.00!!!!!!!!!!!!!!!!

EXHAUST LEAK FIXED AND SO FAR NO CEL'S!!!!!!

This was for a repair that the dealership would cost $3500 for just the parts to replace all cats and o2 sensors, pipes etc.!!!!

Thanks to CuriousB for leading the way for me on this! I owe you one.

I will repost in a few days or weeks with an update.

One final question for CuriousB, DO YOU STILL HAVE HEAT SHIELDS OFF? MINE ARE OFF AND AM UNSURE IF I WILL REINSTALL THEM. I WON'T IF IT IS NOT NECESSARY. THANKS!

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Continued from my previous post on the exhaust leak fix...

Another yellow light that was on and now is cleared (so far) is the yellow check brakes light! So 5 codes in all are now clear.

P0430, P020, CHECK VSC, Traction Control and the check brakes light! My christmas tree has gone dark!!!!!! I hope that I don't have to repost in a few days that they have come back on! So far, so good.

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  • 2 weeks later...

Question for anyone who has done this procedure and had problem solved, DO YOU STILL HAVE YOUR HEAT SHIELDS OFF, OR DID YOU REINSTALL?

Also, Problem still fixed. Simple and inexpensive repair.

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Most interesting topic. My Nissan Frontier has has this code for over 10 years. The code showed up after I installed a Flowmaster muffler. Sometimes I turn it off with my scanner and sometimes it goes off by itself. Luckily, in Virginia, your car will pass inspection with a CEL illuminated.

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  • 4 weeks later...

Question for anyone who has done this procedure and had problem solved, DO YOU STILL HAVE YOUR HEAT SHIELDS OFF, OR DID YOU REINSTALL?

Also, Problem still fixed. Simple and inexpensive repair.

I left my shields off. Its been a >couple years now and my car didn't disintegrate or get hit by a death beam from outer space.

Seriously, the heat shield are primarily to keep the pipe and exhaust gasses hotter the length of the exhaust. When they are hotter they are less dense and have lower pipe friction. So by leaving them off you maybe lost 0.0003 MPG of performance. I wouldn't lose sleep over it.

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  • 1 year later...

I recently got P0420 code on 02 LS430 due to a leak near left O2 sensor right where Y pipe starts. The dealer wanted $3300 to replace cats and entire exhaust. Took it to a local muffler shop which cut and welded a 4 inch pipe right where left O2 sensor is located. Didn't get the code after that. But few days later started noticing high pitch humming noise which was faint in the beginning but with time got louder. Initially thought it might be due to old tires. Last week got new tires and now I can hear the whining noise more clearly now.  It is only there during acceleration and when the rpm goes over 2000. The noise goes away or is hardly noticeable as soon as I remove my foot from gas. The noise is there even in cruise control. Feels like an engine struggling when going uphill except it feels high pitch and doesn't feel like a smooth engine sound. Besides noise the car drives fine.

Took it to back to the muffler shop mechanic but he dismissed it saying that it is just engine sound which can be expected in an old car with 150k miles. It is not very loud but loud enough and high pitch to be really annoying on highway to give a headache. Took it to two other mechanics who could hear the noise but couldn't exactly pin point what was causing it. I feel it has something to do with the welding of new part in exhaust since this noise was not there earlier. Can anyone who has experienced similar issue suggest what it might be ? Should replace the Y pipe with an aftermarket or replace Y pipe and muffler ? It is hard to live with that whining noise. Any suggestions will be highly appreciated.

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