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      08-25-2012, 11:07 AM   #6
Fugly M3
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Drives: 2023 M3CX
Join Date: May 2006
Location: SoCal

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For the e9x cars those that tuned them had a Bavarian Tech (BavTech) code reader that was capable of not just reading the universal codes but BMW specific codes and was capable of clearing them. This is ABSOLUTELY CRITICAL because BMW developed "shadow codes" that are hidden and, if triggered, will tell the dealer that the car has been tuned. There was also a possibility that for cars with BMW Assist these codes were TRANSMITTED TO BMW before they could be cleared. I don't know if that's true or was ever resolved, but the shadow codes are FOR REAL.

For me this was all too much and I just decided against any non-factory tune altogether. Be careful before and after you tune. Just taking it out probably will not be enough. Too many people have had their warranties voided after removing the tune because they failed to clear the shadow codes. Have fun but be careful. The BMW warranty is worth its weight in gold, but its as fragile as an eggshell.
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