Electrical pain in the bum

talukka · 11-01-2025, 07:55 AM

Hello and happy halloween to everyone!

I’ve had a headache with the electronics of my 123d 2011.

About a month ago the car didn’t get any power and was totally black for few hours. Before I had the time to take action about it the power recovered. A little while after that the cars computer informed me that the brake lights weren’t working ”brake light left and right failure”, even tho the both are working flawlessly. Now yesterday ”Charging fault”, so battery is not getting charged.

I did the basic checks: Voltage from battery and alternator. From battery: Off: 12.6V and on 11.6V.
From alternator and the car on: 11.8V

A really probable cause is that the alternator is dead. Before ordering a new one I would like to hear if you got any other suggestions that could be the cause. I’ve got history with cars with major electrical issues and they have made me paranoid and they still make me tweak if I encounter an electrical problem with a car. Thanks.

Any suggestions and hunches are valid for me and I’ll look into them.

ShocknAwe · 11-01-2025, 01:42 PM

Check chassis grounds IBS cable and battery itself. If battery is old just replace it first and start prices with new registered battery.

mkeiser · 11-01-2025, 02:27 PM

also could be voltage regulator rather than the alternator itself.

talukka · 11-03-2025, 03:19 PM

Well I changed the alternator. Charging related problems are now fixed. The brake light failure check control messages are still active. Before the alternator change 44 error codes occured. After the change, clearing the codes and some driving only 2 occured. Those are A8B6 and A8B7. Those two error codes are about the brake lights. To my knowledge the ground IBS could still be the answer to those?

The battery is 4 months old Varta agm and correctly registeted so I wouldn’t worry about that.

Thanks for the replies free welcome to educate me if you have knowledge/ideas.

Fishee · 11-12-2025, 03:40 PM

Lighting issues could be caused by a bad FRM (footwell module).
Given that you've had these issues for a few months, as well as a new battery - the FRM may have packed it in during the battery replacement process.

11-01-2025, 07:55 AM	#1
talukka Registered 5 Rep 21 Posts Drives: BMW 123d Join Date: Aug 2025 Location: Oulu iTrader: (0)	Electrical pain in the bum Hello and happy halloween to everyone! I’ve had a headache with the electronics of my 123d 2011. About a month ago the car didn’t get any power and was totally black for few hours. Before I had the time to take action about it the power recovered. A little while after that the cars computer informed me that the brake lights weren’t working ”brake light left and right failure”, even tho the both are working flawlessly. Now yesterday ”Charging fault”, so battery is not getting charged. I did the basic checks: Voltage from battery and alternator. From battery: Off: 12.6V and on 11.6V. From alternator and the car on: 11.8V A really probable cause is that the alternator is dead. Before ordering a new one I would like to hear if you got any other suggestions that could be the cause. I’ve got history with cars with major electrical issues and they have made me paranoid and they still make me tweak if I encounter an electrical problem with a car. Thanks. Any suggestions and hunches are valid for me and I’ll look into them.
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11-01-2025, 01:42 PM	#2
ShocknAwe 1Addict 5381 Rep 9,254 Posts Drives: N54 E82, M57 E70, 964 C4 Join Date: Jul 2012 Location: Charleston iTrader: (22)	Check chassis grounds IBS cable and battery itself. If battery is old just replace it first and start prices with new registered battery. __________________ 2010 E82 1 Series M Clone Hydra Performance augmented OEM+
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11-01-2025, 02:27 PM	#3
mkeiser Captain 1251 Rep 782 Posts Drives: e82 128i 6mt m sport Join Date: Jan 2022 Location: Minneapolis, MN iTrader: (1)	also could be voltage regulator rather than the alternator itself. __________________ 2011 BMW 128i 6MT M Sport - https://www.1addicts.com/forums/show....php?t=2188535
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11-03-2025, 03:19 PM	#4
talukka Registered 5 Rep 21 Posts Drives: BMW 123d Join Date: Aug 2025 Location: Oulu iTrader: (0)	Well I changed the alternator. Charging related problems are now fixed. The brake light failure check control messages are still active. Before the alternator change 44 error codes occured. After the change, clearing the codes and some driving only 2 occured. Those are A8B6 and A8B7. Those two error codes are about the brake lights. To my knowledge the ground IBS could still be the answer to those? The battery is 4 months old Varta agm and correctly registeted so I wouldn’t worry about that. Thanks for the replies free welcome to educate me if you have knowledge/ideas.
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11-12-2025, 03:40 PM	#5
Fishee Captain 1785 Rep 822 Posts Drives: 135i MSport, GLK350 Join Date: Jan 2022 Location: Toronto iTrader: (0)	Lighting issues could be caused by a bad FRM (footwell module). Given that you've had these issues for a few months, as well as a new battery - the FRM may have packed it in during the battery replacement process.
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