Fault Codes P0430 And P0420 On Ls430

[boblexus430]

I been pondering over some recent fault codes of p0420 and p0430 codes found on my 2001 ls430.

After some investigation I have a solution that can save everyone a lot of money.

1)The codes P0430 and p0420 indicate your catalytic converter efficeniency is reduced.

This would lead one to believe

that the catalytic converter needs to be replaced which can be a major expense since your ls430 has

three catalytic converters. (two forward and one rear) . With a little investigation I found that

the foward exhaust pipe/rear catalytic converter (all one unit) (part number 51868) had a very small

air leak (HOLE in the pipe) hidden under the forward exhaust pipe shield/clamp. This shield is to

prevent your car from catching leafs on fire if you park under a pile of leafs or brush.

Well I said to myself, how did this happen. After further investigation I discovered the lexus cheaped out

on the clamps that hold the leaf/heat shield to the forward exhaust pipe/cat. The clamps had rusted and

become loose which caused the shield to rub a hole thru the exhaust pipe. Well this was interesting.

After some research I found out the forward exhaust pipe cost $1000+ (part alone) from the dealer.

Many people in the internet who had the same problem had their shop weld the pipe for $200+. which is an

exceptable repair. I discovered on ebay

that a replacement part does exist for just over $300 with shipping. The part also includes the four forward

bolts plus the two gaskets. So save yourself a lot of money and order the aftermarket part and rest in peace

knowing that you did not get riped off by your dealer.

PS - you can find the part by typing in the ebay search ls430 51868

This part is good for 2001 thru 2003 ls430's

Details:

I could hear the exhaust leak by putting my car on a ramp. Starting the car while under it at which point

I could hear a leak on the driver side just about 6 inches behind the bank 1 number 2 O/2 sensor.

[curiousB]

I have been struggling with this one myself. I have same pin hole leaks on the Y pipe just under shield. I think electrolysis from dissimilar metals (shield is stainless steel pipe is steel). Poor design. Even entry level Chryslers have stainless steel exhaust pipe. Not sure why Lexus cheaped out here.

I think the shields exist to retain heat in the pipe. This way the secondary catalytic converter gets up to temperature (known as the "light off" temperature)and functions properly.

Unfortunately my 2004 Y pipe isn’t available from after market guys yet.... Only 2003 and earlier. Is $1000 from dealer. Since they tacked on the secondary Catalytic Converter to it the pipe is pricier than it needed to be..

What is odd to me is that

a ) The leak is after the secondary O2 sensor so hard to see why it matters

b ) The exhaust is under positive pressure, the notion of air leaking into the pipe seems impossible if the pipe is positive preesure.

Some of my threads on this saga.....

http://us.lexusownersclub.com/forums/index.php?showtopic=70141

http://www.clublexus.com/forums/ls430/580075-p0104-then-a-p0430-two-days-later.html

[boblexus430]

The shield around the forward Y exhaust pipe is to prevent leafs or debris from catching fire. That is the only

reason for it.

The hole behind the second/rear o/s sensor is causing the o/s sensor to run cooler. the computer

senses the different between the bank 1 forward and rear/back o/s sensor and throws the code.

There are no sensors to measure pressure only temperature difference. The computer is programmed

with a range of codes for each sensor . If an o/s sensor is cooler then it should be a code

is thrown indicating either the cat is clogged or a hole exist in the exhaust. You will get a

diffent code if the O/s sensor is bad.

Try not to read to much into the problem as you do have a leak that needs to be addressed which will cause your car to fail inspection depending on which state you live in.

In your case (2004+ lexus), you will have to remove the Y pipe and have it welded unless you want to pay the price!! Don't reuse the cheap clamps and screws, which to stainless steel.

[boblexus430]

Sorry CuriousB,

Did not read your post prior to responding. Looks like you did your homework. I'll keep you posted

after I get the new Cat in. I see your helpful info on gasket fitting, Perhaps I should go with

factory gaskets. All for now.

[curiousB]

The shield around the forward Y exhaust pipe is to prevent leafs or debris from catching fire. That is the only

reason for it.

Lets just agree to disagree on this one. I am 99.999% certain the shield (and the mineral wool insulation under it) is there to stop the exhaust from cooling so the secondary Catalytic Converter can reach "light off" temperature. Bare uninsulated pipe will cause cooling and delay the secondary converter from kicking in.

There are no sensors to measure pressure only temperature difference. The computer is programmed

with a range of codes for each sensor . If an o/s sensor is cooler then it should be a code

is thrown indicating either the cat is clogged or a hole exist in the exhaust. You will get a

diffent code if the O/s sensor is bad.

I agree there is no pressure sensor but O2 sensors aren't temperature sensors either. They measure the amount of O2 in the exhaust stream. http://en.wikipedia.org/wiki/Oxygen_sensor

It could be the leak stops the sensor from getting to 600° F it needs to function (that's why the sensor has a heater to speed up getting to temp so the engine can jump over to closed loop EFI) but I think it is more likely due to concentration of O2 in the gas after an exhaust pulse pushes through. For a moment it creates a short backdraft (vacuum in the pipe) and O2 is pulled into the pipe and potentially fools the sensor. Anyway there are plenty of posts about the need for this "plumbing" too be airtight so I think a trip to the muffler shop is in order.

[boblexus430]

The shield around the forward Y exhaust pipe is to prevent leafs or debris from catching fire. That is the only

reason for it.

Lets just agree to disagree on this one. I am 99.999% certain the shield (and the mineral wool insulation under it) is there to stop the exhaust from cooling so the secondary Catalytic Converter can reach "light off" temperature. Bare uninsulated pipe will cause cooling and delay the secondary converter from kicking in.

There are no sensors to measure pressure only temperature difference. The computer is programmed

with a range of codes for each sensor . If an o/s sensor is cooler then it should be a code

is thrown indicating either the cat is clogged or a hole exist in the exhaust. You will get a

diffent code if the O/s sensor is bad.

I agree there is no pressure sensor but O2 sensors aren't temperature sensors either. They measure the amount of O2 in the exhaust stream. http://en.wikipedia.org/wiki/Oxygen_sensor

It could be the leak stops the sensor from getting to 600° F it needs to function (that's why the sensor has a heater to speed up getting to temp so the engine can jump over to closed loop EFI) but I think it is more likely due to concentration of O2 in the gas after an exhaust pulse pushes through. For a moment it creates a short backdraft (vacuum in the pipe) and O2 is pulled into the pipe and potentially fools the sensor. Anyway there are plenty of posts about the need for this "plumbing" too be airtight so I think a trip to the muffler shop is in order.

Thanks for the info. One thing I left out. is that codes I'm receiving (Catalyst Efficiency out of range)

are for both sides of the Y pipe (P0430 and p0420 - this was stated in the manual only.

After removing shield clamp on drivers side the leak

sound has increased as it is now noticable when standing 10-15 feet from drivers side.

Prior to that the sound was barely noticable when laying directly under the Y pipe.

I've got to figure out a way to prevent shield and clamps from reacting to the new after

market Y pipe to avoid this from happening again. I was thinking of drilling holds in shield

to allow water do drain, buy stainless steel clamps and screws and paint any rusted areas

as we all know rust makes rust.

[curiousB]

I replaced one of the rusty shield clamps with a 2" stainless steel plumbing gear clamp. Worked well enough to hold shield. Inexpensive too. I wouldn't bother with a drain hole in the shield. That pipe gets so hot when you run car any moisture in the mineral wool will quickly boil off. Probably with a couple minutes of running engine.

I did find the faces of the Y pipe flanges and the mating side on the converter had pockets of corrosion. Now you'll be replacing one side (new flange) to pristene but the other may have some wear spots. Lexus gaskets seem to require a smooth face to compress against. Hopefully you'll get a tight fit.

Keep us posted if the new Y pipe makes the codes go away.

[landar]

My 2002 LS430 has only been thru one (salty)winter. Sounds like I should do a preemptive strike and replace the shield clamps with stainless?

[boblexus430]

This is my update after installing new Y exhaust pipe for 2001 lexus ls430 at a price $304 (Bought from ebay) verses 1200+ from dealer to avoid computer fault codes P0430 and p0420.

New Y pipe came with bolts and gaskets

1) put car on jack stands

2a) Used o/2 sensor removal socket and easly removed both O2 sensors without going into car

2b) use propane touch and 2 pairs of visegrips to remove 4 bolts (2 on each side attached to forward cats)

- heat nuts until glowing orange and remove with visegrips

3) removed rear clamp on Y pipe exhaust pipe. (take extra care to save rear clamp because new Y pipe does

not come with this clamp.) heat with torch put be careful not to destroy clamp

4) wiggled old Y pipe out.

5) cleaned up flanges on ends of two forward cats with wire brushes, cold chisel and hammer

6) bought exhaust pipe seal from pepboys

7) put exhaust seal on cat flanges and around rear of new Y pipe ( you will notice old sealer inside of

pipe you are inserting new Y pipe into) (do not remove old sealer just add new sealer)

8) pushed new Y pipe into rear pipe first

9) install new gaskets and bolts that came with new Y pipe from ebay

10) tightend bolts in front and clamp in back

11) Tested for air leaks by starting car and feeling around

joints between cat and new Y pipe - results: driver side had air leak where

new Y pipe mets cat at bottom of flange.

12a) Loosen bolts on both sides and clamp in back.

12b) Installed small jack under

car on drivers side under Y pipe. Pumped up jack to

force new Y pipe flange and cat flange to meet better with gasket in between, tightened all four bolts and

rear clamp

13) retested and no air leaks

14) erased codes from computer using cheap code reader tool

15) After two weeks of driving no error codes / Fault codes

16) I now HAVE A NEW Y PIPE INSTALLED WITH NO ERROR CODES FOR JUST UNDER $304 DOLLARS

PS: The new Y pipe did not come with heat shields that where on old Y pipe. I did take the time to remove

old heat shields which are in bad shape. the insulation was imbedded in the rust from the old Y pipe and

could not be saved. The heat shields themselfs are not an item you can buy from lexus and after consulting

with several exhaust shops and one automotive teacher the shields are strickly to prevent leafs or debre

from catching fire under car. This being the case I saved the old shields but will not put back on.

During removal of the old Y pipe and heat shields I noticed that old gaskets where shot. Under

the forward heat shield clamp was a 2 1/2 inch rusted thru HOLE IN the Y pipe (up and down),

One could not tell by either hearing or seeing that there was a hole in the y pipe until the

heat shield clamp was removed at which point I could hear the leak in the exhaust!!!!!!!!!!!!!!!

[boblexus430]

Recommendation to prevent from happening again.

I did buy a can of exhaust manifold paint and painted the flanges and new Y pipes. From what I could tell after removing the heat shields, the clamps heat shields and insulation caused the pipe to fail. If you could take the shields off and paint the Y pipe with exhaust manifold paint I think this would prevent this problem from happening. Also recommend replacing 4 bolts and gaskets after cleaning up the flanges.

1) the clamps rusted

2) the heat shields started to rust

3) the insulation trapped water and caused the Y pipe and everything else to rust.

[curiousB]

Well I am still struggling. I fallen into the guilty trap of swapping parts. Forgive me for I have sinned.... I've replaced pre cat O2 sensor. Put in new bank 2 (non OEM) cat. and swapped rear O2 sensors bank 1->2 and 2->1. I experimented with O2 sensor spacers to spoof the ECU system (this did work, I stopped getting the P0430 but then got P0156 instead). I patched a small hole in Y pipe under SST shields with a muffler fiber tape product but that was a laughable fix. I really need the new Y pipe like you but the ebay version stops at 2003 and I'm a 2004..... OEM is >$1000.. Since the most of the parts are the same I'm almost temped to buy the 2003 Y Pipe like you and see if it will fit anyway. The CATs are the same PN.

So I'm going to take one last crack at it this coming weekend. I've ordered all the bolts and gaskets and an going to reinstall the old (OEM) bank 2 cat with new gaskets. I'm going to pull of the whole Y pipe assembly and get it on the bench to see if I can get the holes welded or patched. and then re install.

The new Y Pipe from ebay seems to come without the shields. Did you remove your shield and transfer then over or just not bother? Where I live salty roads are standard all winter. The glass insulation under the shield is just a moist sponge to hold that corrosive salty water (until it boils off, but leaves the salt behind). Seems a bad design. Also I don't know why they wouldn't have used SST for this pipe. It looks like your replacement one is SST. Makes you wonder why an OEM version for >$1,000 can't be as well made as a $300 aftermarket....

Glad to hear you're back in order. Let us know if a P0420/P0430 sneeks back.

I still have trouble understanding why an exhaust leak AFTER the second O2 sensor can play havoc. It just seems that after the second O2 the car doesn't really know what is going on anymore. If someone can explain this I'd love to know. I've heard theories like back pressure and pulses sucking in air but I just picture the pipe always being above atmosphere pressure in my mind.

[diykid]

Recommendation to prevent from happening again.

I did buy a can of exhaust manifold paint and painted the flanges and new Y pipes. From what I could tell after removing the heat shields, the clamps heat shields and insulation caused the pipe to fail. If you could take the shields off and paint the Y pipe with exhaust manifold paint I think this would prevent this problem from happening. Also recommend replacing 4 bolts and gaskets after cleaning up the flanges.

1) the clamps rusted

2) the heat shields started to rust

3) the insulation trapped water and caused the Y pipe and everything else to rust.

[diykid]

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.

[curiousB]

Well my P0430 saga is over I think. Today I removed the Y pipe and secondary catalytic converter section to get it on the bench. I removed the stainless steel heat shields and sure enough on the Bank 2 side the pipe was cracked almost all the way around. The crack was about 6" behind the secondary O2 sensor hidden under the shield. See photos below.

So I reinstalled the Y pipe with finger tight bolts just to get it aligned properly. Then I tack welded the pipe (MIG welder with flux core wire, no gas) so it would stay in the proper orientation. I then pulled the pipe back out and got it on the bench for a thorough welding. It’s really a job for a TIG welder but since I don’t have one I plodded on with my MIG welder. It isn’t a work of beauty but I got the pipe strengthened and plugged up of all the leaks. Then went on to puddle weld the other areas where the shield clamps had existed (and the exhaust pipe was about to corrode through). I figured while I was at it I might as well strengthen those areas.

After I was done I didn’t reinstall the stainless steel heat shields (last photo at bottom) as the fiberglass insulation was damaged beyond use and some of the bumps from welding would have interfered with a proper fit. Maybe someday I’ll get ambitious and put them on but I doubt it’s anytime soon.

I decided to remove the replacement non-OEM catalytic converter I installed back in August and reinstalled the old OEM one. Using new OEM gaskets and bolts throughout, reinstall was a snap. I had bought a new O2 sensor for the Bank 2 secondary side but didn’t install it either. I also didn’t use the O2 sensor spacers I had been experimenting with (spoofing emission system so it didn’t see erroneous bank 2 secondary O2 sensor).

Fired up car and it was immediately more silent than before. Recently the leak had gotten to the point that it was becoming quite audible. Now it was back like it was before all this trouble.

I went for a test drive with my OBDII adapter and laptop. I watched the bank 2 primary and secondary O2 sensors on a graph output.

Lexus LS430 O2 Sensor Graphs.pdf

I knew right away all my P0430 problems were fixed. The secondary O2 sensor was stable, mid voltage range and only moved a little. It closely mirrored the bank 1 secondary sensor. Prior to this the bank 2 secondary sensor tracked the bank 2 primary sensor. That is why I thought I had a bum catalytic converter. I’ve since driven 80 miles or so and no CEL. It might take a couple days to run all the ECU tests but I am very confident this has solved the problem due to the radical change in the bank 2 secondary sensor output after welding the leak.

Lessons learned:

1. This was never a failed catalytic converter problem as some suggested (DAY).
   
2. I am very happy I didn’t buy a $1,000 OEM primary catalytic converter or $1300 OEM Y-pipe/secondary catalytic converter.
   
3. I still don’t understand why a leak well after the second O2 sensor can have such a dramatic impact on secondary O2 sensor readings. While I don’t understand it, I have seen very clearly with leak and without (repaired) leak. The difference is unmistakable.
   
4. I wasted some money on parts I didn’t need. $60 on a bank 2 primary O2 sensor, $175 non OEM catalytic converter, and another $60 on a secondary O2 sensor. I’ll leave the primary O2 sensor in as it’s not worth my time to pull it out. I’ll see if I can sell the slightly used converter and new unused secondary O2 sensor on eBay.
   
5. The design of the Y pipe and secondary catalytic converter is poor. The stainless shield and salt water wicking insulation sets up a perfect corrosion environment for the exhaust pipe to develop leaks. I suspect a lot of LS430 owners will start seeing P0420 and P0430 error codes. My salty home state of IL contributed to my 2004 happening so fast.
   
6. I learned a bit about OBDII and emission control system in general.
   
7. Always use OEM gaskets when removing these parts. The gaskets that came with my non OEM catalytic converter were laughable.
   
8. I made a listening device with 2’ of clear tubing connected to the ear piece of my mechanics stethoscope. It made probing for leaks simple and precise. In fact I found a couple pinhole leaks after I was done that I was able to plug up with a couple of MIG shots.
   

If you get a P0420 or P0430 don’t run out and change catalytic converters. It may be as simple as a pipe crack underneath the stainless steel heat shields.

[boblexus430]

This is BOBLEXUSLS430 with an update to my new Y-pipe installation fix. Working Great!!!!!!!!!!!

Still no error codes (P0420 or P0430) bank one and back two after installing ebay

exhaust y-pipe 2 months back. Save yourself a lot of time and money by ordering this ebay Y-pipe

and take it to your local exhaust shop to have it installed or give it a try yourself.

Make sure you check for leaks on the three connections after installing new Y pipe. If still leaks,

try my jack method on the front two connections and user exhaust sealer on the rear connection.

Don't stop until all the leaks are fixed. don't bother reinstalling the heat shields.

You should be good for another 100,000 miles.

CuriousB's photos look identical to the crack I found on the driver's side under the heat shields.

[curiousB]

This is BOBLEXUSLS430 with an update to my new Y-pipe installation fix. Working Great!!!!!!!!!!!

Still no error codes (P0420 or P0430) bank one and back two after installing ebay

exhaust y-pipe 2 months back.

Same for me. I'm one month later, 1,100 more miles down the road and no P0430 code (or any codes for that matter).

This Y-Pipe and shield is really a suspect design for a luxury car. The pipe should be stainless steel. Also the dielectric junction the stainless shields, mild steel pipe, and mild clamps creates a corrosion environment that any 1st year Mech Eng student wouldn't have designed for.

Anyway this problem is sure to plague many LS430 owners. Save yourself a lot of investigation time and hunt down pipe leaks under the shields first. If your dealer pushes you to a new $1300 pipe go to a muffler shop and have them weld in a patch for $80 as DIYKID suggests.

[jaswood]

Well I am still struggling. I fallen into the guilty trap of swapping parts. Forgive me for I have sinned.... I've replaced pre cat O2 sensor. Put in new bank 2 (non OEM) cat. and swapped rear O2 sensors bank 1->2 and 2->1. I experimented with O2 sensor spacers to spoof the ECU system (this did work, I stopped getting the P0430 but then got P0156 instead). I patched a small hole in Y pipe under SST shields with a muffler fiber tape product but that was a laughable fix. I really need the new Y pipe like you but the ebay version stops at 2003 and I'm a 2004..... OEM is >$1000.. Since the most of the parts are the same I'm almost temped to buy the 2003 Y Pipe like you and see if it will fit anyway. The CATs are the same PN.

So I'm going to take one last crack at it this coming weekend. I've ordered all the bolts and gaskets and an going to reinstall the old (OEM) bank 2 cat with new gaskets. I'm going to pull of the whole Y pipe assembly and get it on the bench to see if I can get the holes welded or patched. and then re install.

The new Y Pipe from ebay seems to come without the shields. Did you remove your shield and transfer then over or just not bother? Where I live salty roads are standard all winter. The glass insulation under the shield is just a moist sponge to hold that corrosive salty water (until it boils off, but leaves the salt behind). Seems a bad design. Also I don't know why they wouldn't have used SST for this pipe. It looks like your replacement one is SST. Makes you wonder why an OEM version for >$1,000 can't be as well made as a $300 aftermarket....

Glad to hear you're back in order. Let us know if a P0420/P0430 sneeks back.

I still have trouble understanding why an exhaust leak AFTER the second O2 sensor can play havoc. It just seems that after the second O2 the car doesn't really know what is going on anymore.

If someone can explain this I'd love to know.

Below...

I've heard theories like back pressure and pulses sucking in air but I just picture the pipe always being above atmosphere pressure in my mind.

Over the past 10 years or so I have had at least two instances of O2 failure indications. After the first one I purchased a new O2 sensor but before I got around to installing it the indication stopped. But when the second one happened I was able to correlate a cicumstance that had just previously occurred.

My Trac system had activated almost repetively/continuously over a short period of time.

Since my RX is not DBW the Trac system uses EFI to dethrottle the engine, starve the engine of fuel. The throttle valve was open to inlet oxygen flow but no fuel to burn so PURE oxygen (20%) reached the HOT sensors.

With a crack in the exhaust pipe nearby the sensors the oxygen rich atmosphere could easily contaminate/"spoil" the HOT sensors when the engine is first stopped.

In my instance the "spoiling" seems to clear with a 100 miles or so of driving.

[landar]

My 2002 LS430 has only been thru one (salty)winter. Sounds like I should do a preemptive strike and replace the shield clamps with stainless?

Just got a chance to look at my exhaust shields/clamps. They actually look ok(I think) at the moment. The clamp bolt is fairly rusted. At this point, would it be better to replace the clamp or just hit the exhaust clamp area with manifold paint? Here's a pic of the LH front clamp. As I mentioned before, the car has only seen one winter even though it is a 2002.

[landar]

My 2002 LS430 has only been thru one (salty)winter. Sounds like I should do a preemptive strike and replace the shield clamps with stainless?

Just got a chance to look at my exhaust shields/clamps. They actually look ok(I think) at the moment. The clamp bolt is fairly rusted. At this point, would it be better to replace the clamp or just hit the exhaust clamp area with manifold paint? Maybe both? Here's a pic of the LH front clamp. As I mentioned before, the car has only seen one winter even though it is a 2002. [Edit] oops. Double 'clutched' on the reply.

[curiousB]

Its hard to say. The place where the pipe rusts through is underneath the clamp and under the SST shield so it is well hidden. I guess if there were a hi temp insulator you could put between the pipe and the SST shield you'd stop the dielectric corrosion that goes on. Maybe some type of hi temp fiber material and won't absorb moisture. Too bad teflon melts at 621 degrees F otherwise a strip of that would be perfect.

The other idea is just to get rid of the SST shields altogether. I didn't reinstall them after I welded up my leaks. I think they exist to keep exhaust gasses hot for two reasons: 1) to allow the secondary CAT to reach "light up" temperature, and 2) to keep exhaust as hot as possible in gaseous state so it has least fiction moving through pipes. So maybe I lost some secondary CAT efficiency and added a bit of backpressure drag on the engine. I don't see a change in MPG so it must be a tiny effect.

[landar]

Well, I could not stand it (not knowing what was underneath) so I pulled the SST shields off to have a look. The bolt holding the clamp just sheared in two, it was so badly rusted. Thats a plus as I did not have to fuss much with it.

Once the shields were off, I did not like what I saw. The pipes were no where near rusted thru but there were some pock marks and quite a lot of residue rust scale. That insulation between the shield and pipe is a mess. And I think it contributed significantly to the extra rust. Trapped heat. Nothing like high temps to cause steel to rust. BTW, I think you are right about the insulation keeping the exhaust hot for the cats.

I decided to sand the Y pipe and paint with Hi-temp paint. I am now in the process of doing the 3 curing cycles for the paint. I have not decided if I will reinstall the shields. I may but not with any insulation. And I bought new SST clamps. I am going to look for some hi-temp exhaust wrap to keep the shield material from direct contact with the exhaust pipe. The paint should help but over time I think it would just wear thru. The following pic is before I painted.

Thanks for the heads-up on this issue, CuriousB. I owe you a beer or two (maybe a single malt?) next time I get to Chi-town. Thanks also to boblexus430!

[landar]

Pic of the finished job. I decided to reinstall the shields (sans insulation). I will recheck it for corrosion each time I drain the tranny fluid.

[boblexus430]

Looks good, Nice work from Boblexus430

[lexusontario]

I have a 2003 LS430 UL. I was getting po 420 and 430 codes. The codes were coming on when the car was at 1200 to 1400 rpm in 4th gear under light engine load. I purchased a new ypipe from ebay and had a muffler shop install it. They said the originaly pipe was stainless steel and they could repiar it if i wanted them to, but I had them install the new stainless y pipe. The technician said that the crack starts where the clamp was spot welded onto the y pipe, even though the y pipe is stainless it still oxidizes just at a slow rate. Myself i will not reinstall the heat sheilds seeing how they cause deterioration of the y pipe.

[hakob83]

Hey guys, I have a 2002 Lexus gs300 and I got the same problem. Have the same p4020/p4030 code low efficiency bank 2. I was told to change the cat converter. I got the aftermarket one and after like 3 weeks the same code popped up:(

I returned that one and got a used but original one from the guy who crashed his car. I had that one installed and got the same code .So I am a little relived now because I found this post, thank you for that. I have been to 3 garages and they could not figure this out.

I remember that one of the mechanics said that I have a leak but they also said that a leak will not cause a cat code come up. Anyway had my car lifted today and I don’t know where is the leak from but i can hear something is leaking. It’s under the heat shield and it’s after the front cat converter, I believe it’s the back cat converter pipe that connects with front cad converter. This other mechanic told me that he can weld the hole but if he takes the heat shield out, it’s all rusted, he will not be able to put it back, and he does not want to leave the pipe without the heat shield as the pipe is right next to gas plastic back feeding pipes and that is why he did not do the work. Do you guys know what I can do besides just buying another cat to replace that piece of pipe?

Can I get just the heat shield or any other ideas what i can do but just buying the whole piece with the back cat converter? I have already spent a lot of $$$.

I really appreciate your help.

Thanks