I did a search and found this...
http://www.e90post.com/forums/showthread.php?t=406772
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>I believe the codes that start with an "A" are light codes. The JB3 is my only mod >and I never have engine/tuning related codes. One day I had a "light out" >warning pop up on my dash and when I BT'd the car, I had several "A" codes pop >up. The goofy thing is that none of my lights were out. I searched around on the >forum and found that there is an SIB (service bulletin) from BMW stating that >there is a known issue with our tail lamps/lamp socket. The warning lights pop up >but no lights are out and this is caused by vibration. There is a fix for this at the >dealer where they will install some foam pads on the housing to dampen the >shock. Not sure if it works as I've yet to take mine into the dealer.
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>I've seen that code on a friends 335i that I've BT'd a couple times.
I'm told >there >is a fan in the electrical box (ebox) where the ECU and the JB3 are >located. I've never looked for it but have heard it mentioned a few times. I >think I've read that the fan blows into the cabin through the firewall to keep the >ebox cool. Did you run the jb3 cable into your glove box through the firewall? If >you did, maybe something happened to the fan during the install.
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