I have a 03 Lexus gs300 I was trying to track down a p430 (only code no p420). I replace all the things possible and it finally went away I replace the cat with a magnaflow 51006 which is a oem grade universal that had to be welded on. I replaced it in August 22 of 2015. The issue I'm having now is the p430 popped back up. I have replaced the bank 2 sensor 2 O2 sensor with denso O2 sensor. I have a ObdII reader and everything is in the green expect my cat. It keeps saying pending no check engine light yet. I checked the reads and my O2 sensor bank 2 sensor 1 is reading .03 to .80 the 02 sensor bank 2 sensor 2 is reading .76 to 78. Could it be the flange gasket needs to be replaced? I didn't do that when I replaced the cat. Could it be the welding job might not have been completed properly? Anyone have any suggestion thanks for your help in advance

 

Ipacrkcars,

Please check your Y pipe that is after the header like people call but I call it, Catalytic Exhaust Manifold. LOL Again, go to any muffler shop and ask to the tech to check the small catalytic before two mufflers. Mine was clogged and start giving me the same code that you have right now.

 

My OEM mod pipe or Y pipe that was clogged





This was part of the crap that come out. I change the Y pipe and my car come back as was before and the more important. NO MORE CODE.

 

Thanks for the response. How much did that y pipe run you or can it be cleaned out? I need to get my car inspected asap

 

I found a original one, used one, with low miles on it and the guy want $200.00 and 3 hrs to go and get it. LOL But still work perfect on my car. I see that to many people just tell to the muffler tech., cut it and add just a pipe there. But, I don't if later on the cel go ON or not. How knows?

 

So do I need to just replace the y pipe and not the small cat? I heard the small cat is a bank 1 read?

 

You ask me two question?

First one, What the muffler guy need to do is, cut that small cat pipe and add a small pipe and you'll be okay. That is what I see that the muffler guy do all the time.

Second one, NO, NO, NO.... That is not the bank 1. Is the third one or just the small one and the last cat
.
Piston 1,2,3 is Bank One or Cat One and Piston 4,5,6 is Bank 2 or cat 2. Our car have 4 O2 Sensor, 2 in each Bank or Cat. One sensor before the cat and one after the cat. In part on the dealer, the tech calling each cat, by the location of the piston. Again, Bank 1 Position 1 to the O2 Sensor that is before the cat. Bank 1 Position 2 is the O2 Sensor that is after the cat. To the second Bank, is Bank 2 Position 1 before cat and Bank 2 Position 2 after the cat. But by the last cat name is just the last cat or small cat. No have a name location or position. I hope and this help you to understand just a little more.

 

Ok. I have one more question thanks for you help. So that y pipe can be created by a muffler shop? Or should I just go to the junk yard and try to find one in good condition?

 

You can go to the junk yard and found one in good condition. But made sure have low miles, no was to much time on the junk yard exposed to the different temperature change. Raining, Hot temperature, cool weather, snow, ect. May sure look fine also, that way you know that is good to use.