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      04-20-2012, 08:51 PM   #2
First Lieutenant

Drives: 2006 330i E90
Join Date: Aug 2011
Location: So Cal

Posts: 343
iTrader: (0)

Yes, the blue wire should be connected. That is how ECU communicates to the IBS. If IBS itself has gone bad which is located directly on the negative terminal, then the car may not start. Often, taking that blue connector out temporarily, may start the car since that stops communication between ECU and IBS. Also, if you ever need to remove IBS to change battery, be very gentle since it is sensitive to mechanical stress and changes its calibration point needed for accurate measurement of battery charge characteristics and its history.