LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

Check Engine Light Code PO420 PO430

Old 10-26-12, 02:31 PM
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It is possible that the cats you have are new but of poor quality.
it is not uncommon for shops to install the cheapest cats as a cost saving measure as quality cats cost a lot of money due to what is inside of them. Plus the factory cats typically can have a very high scrap value, so less reputable shops will replace factory parts with junk parts, recoup a large amount of their cost back with the scrap value and net more money on the job.

That said, the cheap cats are usually very small and/or universal fit and need to be welded in place so they are easier to spot...

Originally Posted by LScowboyLS View Post
to repeat -
100+ trips to a muffler shop in your life time???
i really hope you are 50+ to justify a number like that.

Call me crazy but if you have the ability to do the work yourself, you have the ability to check it out yourself. The 10mins of time it takes to check it yourself, verify and fix the problem is very rewarding for many people. Not to mention the act of wantonly wasting a business' time without compensation, when you have no intention of them doing the repairs in the first place, is less that ethical. That sounds like something a 17y/o kid would do, not an adult. It may very well be how they generate business but it is a pretty slimy way to take advantage of a service.

If you disagree with that, thats fine but i'm coming from the other side of the coin, in saying that I'm sure you would hate if a customer or a client knowingly wasted your time and resources to have you do the legwork before they up and took their business to another firm or stole your work and did it themselves.

if you go in and state that you just need them to check it so you can do the work at home, with full intention of paying for their time, thats a different story...

I dislike people wasting my time.... I'm sure you do too.
and i HATE people who knowingly waste my time.
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Old 10-26-12, 06:20 PM
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Originally Posted by DK Audio View Post
Wow, interesting. I didn't find any leaks either so I was thinking it is the cats. So if you just have straight pipes welded in then I assume I'd still throw codes? I'm not in an emission testing state.
Yes, straight pipes are going to put you in a closed loop mode and hurt your mileage and power. If anything, I bet the power reduction from running rather rich, as PD mentioned, negates any power increase from removing the cats. You need 02 simulators to fix this. I was considering this but since the exhaust shop stood behind their work and fixed the problem everything is fine now.

Here is a link to the ones I was looking at.

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Old 11-19-18, 08:01 PM
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Default Replace O2 sensors

Originally Posted by DK Audio View Post
My check engine light came on and I read the codes, they are PO420 and PO430, the generic OBDII description is "catalyst effeciency below threshold." Any idea on what do I need to do for this?
I have a RX330 2004 model. I have the same two codes with over 279,000 miles. Everyone (four auto shops) said I need a new catalytic converter, two might I add, and nobody wanted to properly diagnose the cause for the code. Catalyst system below efficiency does not mean you need a catalytic converter. It means something that is part of your catalyst system is faulty. Mechanic by the name of Wes with Ben Bookout Auto Repair in Hiram GA took his time and tested the voltage of the O2 sensors and found that 3 sensors were reading too high. He replaced all four sensors with denso only parts and both codes went away. I'm 250 miles in since my repair and my check engine light has been off and I passed my emissions with flying colors. A $600 investment is lot cheaper than a $3,900 unnecessary repair cost in which your CEL would still come back on if you dont get your car diagnosed first, not just scanned with an OBD scanner. Always go with the cheapest route first my dad taught me and you replace 1 then replace them all. Hope this helps!

Last edited by TashaRRT13; 11-19-18 at 08:03 PM. Reason: Misspelled
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Old 11-20-18, 07:26 AM
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Originally Posted by Shmee View Post

if you go in and state that you just need them to check it so you can do the work at home, with full intention of paying for their time, thats a different story...

I dislike people wasting my time.... I'm sure you do too.
and i HATE people who knowingly waste my time.
I like you.

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