Just got a check engine light on my 99 TL and when I checked the code with my scanner, I got a code P420, which suspects a failure of the catalytic converter. I was told that a TSB 03-027 exists, which has information about this problem, but I can't seem to find a website where I could read the TSB. Can anybody help me here or at least give me some info about this problem. My car has 106K miles, but I have no idea how long converters usually last. I have never had to change one in my life, so I guess they would last longer than 8 years. Research on replacing a converter estimates the cost at nearly $800 to replace it. Panic has set in!

 

You can most definitely replace it for less that that. You can buy the Random Technology hi-flow catalytic converter from our vendor Josh (Excellerate) for just over 225.00 You'll save even more money installing this yourself. It's not hard.

 

I have my old cat that is still good, i replaced it with a high flow one. If ya want it, PM me.
The dealer will try and rape you to replace it with a brand new OEM one.

 

You can also have other problem leading to cat failure
Codes are not diagnosis- just hints
A muffler shop can do actual test on the cat itself

I have had them go anywhere over 50k miles- the Federal standard at the time
Once out of warranty- good luck
Check local muffler shop for legal replacement that passes smog and fits your car
Run some Seafoam too- see thread Seafoamed the Ol Tl
for tips

 

If you go to a hi flow- sometimes you have to install a spacer for the O2 sensor so it still gets correct reading

 

That code often comes up wit a bad O2 sensor (ones thats reading wrong) or when the egr ports or egr are bad. You should have other things looked into before dropping that type of money in a cat

 

Oh and i have 230k + on my original cat

 

Thats what I was thinking when I said codes are not diagnosis- and since our moderator really knows these cars- now we have the answer.
The TSB ~may~ have been about cleaning the EGR ports, they get severly plugged and -99s seem to have it alot based on threads here
See threads on removing intake and cleaning egr passageway- takes a couple hours
The 02 sensor- the other likely cause- can be tested with a multimeter and removed and inspected for clogging