Perfect timing - PeachParts Mercedes-Benz Forum

2.5Turbo · #1 04-09-2010, 01:47 PM

A few weeks ago the check engine light came on in my Subaru. I had just dropped about $900 on it at the shop two weeks earlier getting a rusted out exhaust replaced and a number of other things done to it, so I wasn't all that happy when it came on. Got it scanned at Autozoo recently and it showed a P0420 - exhaust catalyst efficiency below threshold. Damn, my cat went bad...time to spend another $900

So since my car is an '02 and has under 80,000 miles, I decided to go check if there was any warranty left on the emissions system. While the car was manufactured in August 2001, it was sold in April of 2002, 4/24/02 to be exact. I had about 20 days and less than 3,000 miles left on the warranty! Needless to say I've got it scheduled at the local dealer for Tuesday

I've read around and found out that it could be a faulty front oxygen sensor, but that shouldn't be a big deal it's bad because they're a lot less expensive than a new cat.

okyoureabeast · #2 04-09-2010, 01:55 PM

Did you see that 300SD for sale down at the used car dealer near the Hampton Inn? I'm pretty sure he still has that and a w126 for sale as well.

I also know of a guy in Dryden too who has a Euro TD that he is going to repair and re sell too.

Jim H · #3 04-09-2010, 04:12 PM

Quote:

Originally Posted by 2.5Turbo

...Got it scanned at Autozoo recently and it showed a P0420 - exhaust catalyst efficiency below threshold. Damn, my cat went bad...time to spend another $900

Well, hold on, not so fast. I had an "exhaust catalyst efficiency below threshold" type of problem several times, but it was never the cat... Bad spark plugs and 'leaky' spark plug wires produced this code twice. ANY regular misfire can overload the cat just enough to trigger this code. In my case, new plugs made it go away within 8-10 engine start-stop cycles. I came back, and a bad wire made it go away again...

Before you drop $900, be SURE it's the cat!

2.5Turbo · #4 04-09-2010, 06:56 PM

My indy is pretty sure it is. I had him clear the code last Friday and he said it's most likely the cat if it came on again. He says he usually stocks three cats at any given time since it happens more than you'd think. It came on again a couple days after he cleared it and hasn't gone away all week. I had the plugs replaced a few weeks before the code, but I haven't noticed any misfires or issues that would indicate a bad plug. The dealer's going to do tests to make sure the cat's bad anyway, and if it is bad it's not my dime anyway.

Adam - I did see that 126. I think it's been there a while. You saying I should dump the Subaru and pick up another Benz?

cmbdiesel · #5 04-09-2010, 09:23 PM

Hey, if you can get a new Cat right on the outer limit of the warranty, go for it. Doesn't matter if it's failed or not, it will eventually need replacing, and doing it under warranty (early or not) is definitely the way to go. If the check engine light returns, well, at least you have a shiny new Cat...

cmbdiesel · #6 04-09-2010, 09:25 PM

Quote:

Originally Posted by okyoureabeast

Did you see that 300SD for sale down at the used car dealer near the Hampton Inn? I'm pretty sure he still has that and a w126 for sale as well.

OK...I'm confused... he has an SD AND a w126 for sale???? Does he also have a 300D and a w123 ??

Chas H · #7 04-09-2010, 09:30 PM

Quote:

Originally Posted by Jim H

Well, hold on, not so fast. I had an "exhaust catalyst efficiency below threshold" type of problem several times, but it was never the cat... Bad spark plugs and 'leaky' spark plug wires produced this code twice. ANY regular misfire can overload the cat just enough to trigger this code. In my case, new plugs made it go away within 8-10 engine start-stop cycles. I came back, and a bad wire made it go away again...

Before you drop $900, be SURE it's the cat!

I had the P0420 code shortly after the coil pack failed on my Miata. It was, unfortunately and expensively, the cat.
A good scanner can readout the voltage outputs from the 2 O2 sensors in real time to help identify the true cause of the code.

okyoureabeast · #8 04-10-2010, 03:32 PM

Quote:

Originally Posted by 2.5Turbo

Adam - I did see that 126. I think it's been there a while. You saying I should dump the Subaru and pick up another Benz?

Duh. Do you want to be a typical college student driving a Subaru or a college student driving a Benz

I gave some kids a ride and they were like, "Holy crap! You're the guy that owns this car? I see it all the time on campus!"

@cm He only has the w126 and the SD. The other guy I mentioned lives in Dryden. He has a wagon and some other cars. Go ahead and look him up. http://maps.google.com/maps?q=dryden+ny&oe=utf-8&client=firefox-a&ie=UTF8&hq=&hnear=Dryden,+Tompkins,+New+York&gl=us&ei=PNLAS-fHPMH98AaltLmWBQ&ved=0CAgQ8gEwAA&ll=42.490161,-76.307023&spn=0.002191,0.005681&t=h&z=18

He lives at 92 West Main Street.

2.5Turbo · #9 04-14-2010, 12:49 AM

Don't think the parental unit who owns half the car would agree to such a trade

Anyway, the dealer checked it out today. I think they tested cat with the car on the dyno because there were about 15 more miles on it when I got it back...they better not be taking it out to lunch

. They concluded the cat in fact was bad and a new cat is on its way for a Thursday appointment. They're also doing some recall work on a corrosion issue with the rear subframe, it's basically a clean and undercoat job. And they shuttle me to and from school. And they have a cooler full of ice cream bars in the waiting area

. Although I won't be taking it there for normal service based on the amounts I was hearing other people were paying...