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2003 BMW 325i
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25 Posts
Discussion Starter · #1 ·
Unfortunately the day has come when my cats have gone bad. From the looking that I've done, it's quite expensive to get these replaced. I was thinking a potentially cheaper solution would be to replace the headers with the Active Autowerke headers, as well as some after market catalytic converters. One potential issue I see with this is the O2 sensors, and possibly some engine codes. I'm not sure if this has been done before, but has anyone done this? If so, any tips? Would also love if y'all could point out other potential issues with this fix, or other fixes you've done yourself. (I would like for my car to still pass emissions is what I'm aiming for).
 

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Administrator
2004 330Ci 115k miles
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16,704 Posts
What is the production date on your 2003 325i?
If it is before 03/2003 then you have MS43 DME and can simply flash in the EU2 software to remove requirement of post cat O2 sensors and SAP system. Many have already done this. Of course, your local smog check may be an issue depending on where you live.
 

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2003 BMW 325i
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25 Posts
Discussion Starter · #3 ·
If it is before 03/2003 t
It is 06/2003. Just figured out a loophole that says I don't technically need to get my emissions inspected since I am an out of state student. I'd still like to keep it legal if at all possible however.
 

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1,917 Posts
With Bali's help, I flashed the EU2 tune on my '03 530i...I was getting cat-related codes, but they are not clogged. My car runs great after the flash, but I lost my check engine light in the process, which apparently is common. The check engine light will not illuminate when the key is turned to position 2 nor when there is an actual error.

I did this about 10 months ago and now need to get inspected.. in my state, MA, they don't check emissions on cars built before 2005, but I worry my inoperative check engine will cause a fail. I will try to update this after I get it inspected.
 

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Registered
2003 BMW 325i
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25 Posts
Discussion Starter · #5 ·
Just an update for those that care, I ended up going with Catless headers and SAP delete. I got a cheap tune form Active Autowerke, however since I have the MS45, and no post cat o2 sensors, I have a constant check engine light. As I was also saying, I found a loophole allowing me to go without getting emissions checked. (I am a college student that lives out of state, and out of my cities "smog area". Since the state I go to school in, Alabama, does not require emissions, I just submit a yearly waiver and get my registration renewed without having to get emissions checked.)
 
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