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Discussion Starter #1 (Edited)
I was searching here for the same issues, but did not get any results, and was hoping some of the technical gurus could point me in the right direction.
This is regading my 2010 m5 with roughly 15k miles, the only mods are RPI GTS exhaust and i recently removed the charcoal filters.

Drove the car to work today, came out around noon to go to lunch, and when i hit the start button, the car would not start. Hit the start button again, the car fires up, but the dash lit up with every known worning message; check engine, trans malfunction, lights, airbag restraint, reduced power, etc. The navigation screen was off, the radio and climate controls were off, the seat and steering wheel would not adjust, the car idled rough. I shut it of and started it up again, but the same issues persisted. I shut the car off again and decided to disconnect the battery, and when i got to the trunk, i noticed that my break lights were on. Weird. Disconected the battery for 10 minutes and the car fired up with no wornings or issues. Drove it home with no issues, it actually felt more responsive and faster.

Tried googling the symptoms and the only post i found that was somewhat relevent was on bimmerfest where a 7 series owner had similar issues and repaced the Integrated Supply Module and the issues went away. Do our cars have this module?? As always, any help would be greatly appreciated.
 

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Discussion Starter #3
I would start by checking the voltage on the battery... A bad battery or one going bad can cause alot of issues on this car..
I will, but the battery was checked about a month ago, when the car when in for service for another issue. Plus it cranks easaly..

Thanks for the input.
 

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I would start by checking the voltage on the battery... A bad battery or one going bad can cause alot of issues on this car..

Same thing happened to me as the OP and once I upgraded to a new AGM, the problem went away.
 

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I will, but the battery was checked about a month ago, when the car when in for service for another issue. Plus it cranks easaly..

Thanks for the input.
I bet your voltage regulator/alternator is failing -- which is VERY common -- it will kill your good battery quickly.

There are several threads and a DIY by SoCalE39 on how to replace the voltage regulator/alternator. Very easy fix.
 

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Discussion Starter #6
I bet your voltage regulator/alternator is failing -- which is VERY common -- it will kill your good battery quickly.

There are several threads and a DIY by SoCalE39 on how to replace the voltage regulator/alternator. Very easy fix.

I had this happen on my 07 M5 where I had to replace the voltage regulator on the alternator, but all the symptoms happened while the car was running and in motion, which makes sense because the alternator was running. The symptoms I described in OP start before the engine turns over right after I hit the start button. Therefore, I would rule out the voltage regulator.

I also do not believe it is a battery issue since I measured the voltage, and it is around 12.7V before starting the car, and the car cranks freely and strongly. It feels like a faulty transistor in one of the modules that resets itself after I disconnect the battery for 5 minutes or so. If anyone could let me know which module would be responsible for the described symptoms, I'd be willing to swap it out.
 

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I doubt it's a module at all.

First off, to verify the battery isn't the culprit, measure the voltage using an analog voltmeter *while attempting to start*. The load placed by the starter will drop voltage by some amount, regardless if it's a brand new battery or not. If the battery is defective or has low capacity, the voltage will drop significantly (below 11V).

Next, do the same thing at the starter positive cable connection point under the intake plenums. This is often loose and causes similar problems.

For that matter, check all cable connections in the trunk, the firewall penetration in the trunk, and the positive terminal jump start point under the hood.

If you can read codes, see if the CAS module is logging a terminal 50 error.
 

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Discussion Starter #8
I doubt it's a module at all.

First off, to verify the battery isn't the culprit, measure the voltage using an analog voltmeter *while attempting to start*. The load placed by the starter will drop voltage by some amount, regardless if it's a brand new battery or not. If the battery is defective or has low capacity, the voltage will drop significantly (below 11V).

Next, do the same thing at the starter positive cable connection point under the intake plenums. This is often loose and causes similar problems.

For that matter, check all cable connections in the trunk, the firewall penetration in the trunk, and the positive terminal jump start point under the hood.

If you can read codes, see if the CAS module is logging a terminal 50 error.
Thanks! I will measure the battery output while starting the car, and will also check the other connections.

As far as the starter positive cable under the intake, is that easily accessible or do I need to remove the plenum to get to it?

I only have a basic ODBII reader.
 

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Thanks! I will measure the battery output while starting the car, and will also check the other connections.

As far as the starter positive cable under the intake, is that easily accessible or do I need to remove the plenum to get to it?

I only have a basic ODBII reader.
Plenum has to come off.

As for reading codes, you need BMW specific software, to read the codes. Specifically you are looking for an A050 from the CAS module.

A dealer should be willing to scan the codes for you and share them.
 
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