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Old 12-30-2012, 10:53 AM
bimmerfan52 bimmerfan52 is offline
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Location: Arizona
 
Join Date: Feb 2012
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Mein Auto: 545i
Quote:
Originally Posted by spiderman3k View Post
Interesting. The good news that I took the risk and I took off on a road trip with my BMW. I started this morning about 8 am and drove foe 1200 miles.. the problem only occurred once at 8:05 lasted for about 10 minutes and that was all.! I'll try the little guismo that bimmerfan52 was mentioned.. before ordering the new alternator.. I already order the mpm(micro power module) while I wait for that device I'll try to check the voltage and see what happen.. but like in said did only once in 1200 miles.. when these problem appeared i can definitely see and feel the difference.. the tranny if I'm on highway will stay in higher gear but if I'm in the city and these event happen .. won't pass the 1 st gear and won't shift. No power to then windows .electric seat won't work mirrors heat or a/c etc but I
The high beam turn signal and sometimes the radio with work.???? I know weird.....! Like I explained before only last for 5-10 minutes BUT if I turn the car off between that time frame it wont start back on.. I'll need a jump start.. on the other hand when I got the power back meaning. When the I-drive and blower fan and all the electrical seem that is back except for the tranny. The tranny won't shift normally after I stop the car and turn it completly off then immediately I can start the car ...ALL the check engine lights and errors will go away and the car WILL run like a champ after those 10 minutes of breakdown.. its freaking crazy that's why I'm sceptical about alternator...and more inclined thorst the mpm ( micro power module)
I suppose there is a chance that your MPM is malfunctioning but I doubt it. Instead I believe your MPM is working perfectly and doing its job in protecting your cars electrical system due to undervoltage (remember, in an electrical circuit, when voltage drops and the load remains the same more current is supplied as demanded by the load. Excessive current can destroy electrical components).

In the BMW electrical system part of the MPM's function is to control relays which selectively shutdown load, normally during starting to make the battery work less hard, but also in response to undervoltage or overcurrent in the electrical system.

The attached PDFs are two of my favorite resources for understanding and trouble shooting BMW electrical systems. You will want to read through the entire Energy Management PDF, but first go to pages 29 and 30, which discusses the MPM function and its control of the relays (specifically 30g to shed system load), and pages 27 and 28, which outline the load/consumers controlled by the 30g relay.

The other PDF outlines the distribution of power to the car.

Good luck with troubleshooting your system. The plug-in voltmeter is a great tool for any vehicle as you can easily view voltage during startup and while driving.
Attached Files
File Type: pdf BMW Power Systems -Energy Mgt.pdf (6.56 MB, 271 views)
File Type: pdf BMW Power Systems - Power Supply Smaller.pdf (1.83 MB, 277 views)
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