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7 Series - E65 / E66 (2002 - 2008)
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  #1  
Old 10-15-2012, 12:38 PM
MunecoBx MunecoBx is offline
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Mein Auto: 2003 BMW 745Li
BMW 745Li Low Voltage Troubleshooting

Low voltage issues on a 7-Series can cause all types of issues which can be misleading. Yesterday, I had my car stutter and the following errors showed up:

1. Brake and drive control systems malf..Parking brake without emergency braking function. Avoid hard braking. Please contact the nearest BMW center.

2. "Driver side window not initialized" and does not flow continuously.

3. Airbag sensor

4. Check Engine Lamp due to "Emissions-related fault"

5. Brake lamp and interior lamps flickering

6. Transmission "fail safe mode"

Those are the ones I could remember. From reading through all of the forums I came across many different type of solutions which related to the "battery" and "alternator." So I took it to the BWM dealership and they said I needed to replace both the battery and alternator. I doubted this so I took it to a local Autozone who also tested it for me and they both tested "good." I was lost because I didn't want to invest that much money in replacing both if I'm being told that both are good. I know how the dealerships work after being robbed so many times by them.

I took it to a 3rd mechanic for a final option. He tested both the battery and alternator and both tested good. But he wanted to inspect the terminals on the battery closer for whatever reason. Upon doing so, he noticed that there was a small amount of acid or residue which leaking from the positive terminal. He immediately said that even though the battery is showing a "good test," it needs to be replaced. But that he felt confident the alternator was OK.

I asked him if I should go to AutoZone/Western Auto and get an after market battery for a cheaper price and HE QUICKLY SAID NO. He recommended I get the BMW OEM battery due to the vast amount of electronics this vehicle has. Especially since the Logic 7 has so many issues related to current.

I went ahead and purchased the battery with his discount for $266. Installed it, MUST BE REGISTERED TO THE VEHICLE, and it took care of all the faults and every problem that existed.

THE MORAL OF THIS STORY, A LOW VOLTAGE BATTERY CAN EVEN TEST TO BE GOOD BUT SHOULD BE FURTHER EXAMINED AS ANY LEAK COULD CAUSE ALL SORTS OF CRAZY MISDIAGNOSIS. ANOTHER MORAL, DON'T TRUST THESE DEALERSHIPS!

Good luck!
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Old 10-15-2012, 03:45 PM
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wjjklj wjjklj is offline
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Mein Auto: 2009 750i
Keep an eye on it. Alternators can also give a good reading and randomly drop low voltage or high voltage. Was your battery original?
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Old 10-16-2012, 05:35 AM
MunecoBx MunecoBx is offline
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Mein Auto: 2003 BMW 745Li
Low Voltage

Thanks for the heads up. Yes, the battery in car was original and so is the new one. Appreciate it.
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