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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Thu, Jun-04-2009, 05:09:29 AM   #1
carter510
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Default 2003 m3 catalytic converter problem

i recently took my e46 m3 to the dealership for a check engine light, they told me that they needed to re-flash my ecu because i was running too rich. after the re-flash the check engine would not go away and i was told that i need to replace my catalytic converter. i called around to see how much it would cost to replace my cats and was quoted between 3-5k for parts and labor. do i need to buy a factory catalytic converter or can i buy an aftermarket cat and have it welded on? has anyone else had this problem?
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Old Thu, Jun-04-2009, 05:59:14 AM   #2
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The cheapest route is buying some OEM headers off someone who has gone aftermarket. Then pay someone to swap them. I'll sell you mine for a hundred bucks.
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Old Thu, Jun-04-2009, 06:08:42 AM   #3
MarqE46
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This seems to be a common problem on E46 M3s. I believe there is a recall on SES light reading false bad cats code. Another alternative would be going catless ebay headers with o2 simulators so you wont throw a SES light on the dash + more power + more aggressive exhaust sound.
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Old Thu, Jun-04-2009, 01:51:27 PM   #4
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Buy someones OEM cats. In California they check the cats now at the SMOG station. Some folks around here are in for a rude awakening. The car running rich would have shortened the life of the cats.

Jumbosock, I'll take yours off your hands, PM me and we'll deal. I want to sell them to carter510 and turn a healthy profit.
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Old Thu, Jun-04-2009, 02:03:57 PM   #5
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How many miles do you have on your M3? It may be covered under the 8yr/80K mile emissions warranty.

I just had mine replaced this way last month. "Saved" me $4K-$5K at dealer shop rates.

If not, I would just buy some slightly used headers for cheap like the others said and have someone bolt them on. Keep in mind that OEM remanufactured headers/cats cost about $3600 for a full set...so I'd take up the offer for $100 if they're in good condition.

To answer your question, No, you can't simply weld on new cats on a stock exhaust system because they're part of the headers.
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Old Thu, Jun-04-2009, 02:29:27 PM   #6
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Quote:
Originally Posted by itchyn View Post
How many miles do you have on your M3? It may be covered under the 8yr/80K mile emissions warranty.

I just had mine replaced this way last month. "Saved" me $4K-$5K at dealer shop rates.

If not, I would just buy some slightly used headers for cheap like the others said and have someone bolt them on. Keep in mind that OEM remanufactured headers/cats cost about $3600 for a full set...so I'd take up the offer for $100 if they're in good condition.

To answer your question, No, you can't simply weld on new cats on a stock exhaust system because they're part of the headers.
My '01 with about 90k miles threw engine code, needed cats. Quote was about 5k, and I'd be selling the car before paying 5k for some cats. I inquired with BMW NA about potential coverage under the 8yr / 80k fed emissions warranty, knowing full well I was out. They said get diagnosis confirmed at dealer, which I did, then dealer offered to cover parts under "good will" even though out of warranty. I paid labor to install new headers and cats (about 1k), plus I opted to pay for new O2 sensors same time given my mileage (about 1k).

So it was generous, but in hind sight, I'd probably go with some euro headers and in-line cats just to get the better sound and performance. So, if you can't get any warranty coverage, then I'd either (a) buy some used but low mileage OEM's from this forum, which will still run ya some good labor costs for install, and think about O2's also, or (b) install some good aftermarket headers and cats...

Regarding "weld ins" - I have heard some shops may offer this, via cutting out old cats and then just welding in new ones, but have no experience and heard you would be well-advised to get some type of warranty from such shops in case you throw same cat engine codes again...good luck
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Old Thu, Jul-21-2011, 04:41:25 PM   #7
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Default Re: 2003 m3 catalytic converter problem

Quote:
Originally Posted by itchyn View Post
How many miles do you have on your M3? It may be covered under the 8yr/80K mile emissions warranty.

I just had mine replaced this way last month. "Saved" me $4K-$5K at dealer shop rates.

If not, I would just buy some slightly used headers for cheap like the others said and have someone bolt them on. Keep in mind that OEM remanufactured headers/cats cost about $3600 for a full set...so I'd take up the offer for $100 if they're in good condition.

To answer your question, No, you can't simply weld on new cats on a stock exhaust system because they're part of the headers.
Man, You are the best!!! My smg stopped shifting yesterday as I was driving. I was terrified as to how much this might cost. The car was towed into Fairfax BMW, and after a shift relay being installed ($350) which was a required first step to determine what was wrong, they said my check engine light was not just coming on due to transmission issues, but the CAT's. They also quoted the $4-6K price to replace. Today, they said the hydraulic pump on the SMG was bad and it would be $3500. I mentioned your note about the warranty on the CAT's and they called back and said they would replace them under warranty! If I hadn't read this and brought it up, they wouldn't have done this at all. You just saved me the $4-6K! Thanks!
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Old Thu, Jul-21-2011, 06:09:56 PM   #8
calvinf1
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Default Re: 2003 m3 catalytic converter problem

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Originally Posted by Waynedude View Post
Man, You are the best!!! My smg stopped shifting yesterday as I was driving. I was terrified as to how much this might cost. The car was towed into Fairfax BMW, and after a shift relay being installed ($350) which was a required first step to determine what was wrong, they said my check engine light was not just coming on due to transmission issues, but the CAT's. They also quoted the $4-6K price to replace. Today, they said the hydraulic pump on the SMG was bad and it would be $3500. I mentioned your note about the warranty on the CAT's and they called back and said they would replace them under warranty! If I hadn't read this and brought it up, they wouldn't have done this at all. You just saved me the $4-6K! Thanks!

Wow did they really charge you $350 bucks to change the SMG relay? That relay cost $10 to buy and 10 minutes to swap with one torx tool.
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Old Thu, Jul-21-2011, 11:49:06 PM   #9
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Default Re: 2003 m3 catalytic converter problem

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Originally Posted by carter510 View Post
i recently took my e46 m3 to the dealership for a check engine light, they told me that they needed to re-flash my ecu because i was running too rich. after the re-flash the check engine would not go away and i was told that i need to replace my catalytic converter. i called around to see how much it would cost to replace my cats and was quoted between 3-5k for parts and labor. do i need to buy a factory catalytic converter or can i buy an aftermarket cat and have it welded on? has anyone else had this problem?
Did you have the engine light on for awhile? You have to be running rich for a long while before damaging the cats.

How many miles do you have?

You can also run a smog test and see if the numbers are way off. If not, the cats are probably still working.
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Old Fri, Jul-22-2011, 02:10:34 AM   #10
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Default Re: 2003 m3 catalytic converter problem

How many miles are on the car?
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Discussing 2003 m3 catalytic converter problem in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)