What could be the problem?

[Migibizzle@hotmail.com]

Hello, everyone well recently i had my check engine light come on. I read the code and i got a "1231". I changed the battery but still had the check engine light on. But i noticed one thing. At idle the light would turn on. But as i pressed the accelertator the engine light would turn on. But not only that the interior dash lights and electric seats would stop working at this point. But if i passed the 2500 rpm mark the check engine light would turn off and everything else would begin to function correctly. Today i was drving around and all of a sudden my car died on the road. The battery had drained (new battery) I assumed it was my alternator that was not working. So i decided i would jump the car but figured i would not get far because the alternator was failing. Not the case i drove th car in manual mode to keep the rpm's up. The car made it without a hitch. I have turned it on twice already and everything seems to be normal ( seems like the alternator is passing charge) Could it be the alternator or something else like the DME relay? what do you guys think. Thanks for any help.

[shogun]

Pls do everybody who wants to help you one BIG favour: indicate built year and month, model, has the car automatic or manual gear, which engine, and more other details. There are 7 series models such as E23, E32, E38, E65, E66.
And each of them has a special design, engines and country version.
Just use on top the user CP and indicate your model with details and it will always be in your profile, and if you do not know when your car was built, use my website and see under VIN decoder.
Sometimes even the month of a year is important to see what kind of MOTRONIC it has or which country version etc.

Also more details, the more the better:
did you check with a multimeter all the time the voltage?
what is it at engine off and ignition off, at ignition on, when cranking, at 1.500 RPM and at 2.500 RPM, as you say that solves the problem.
Have you checked the belt? Maybe slipping? Belt tensioner?
Go for the alternator checking first, DME seldom is damaged.

[Migibizzle@hotmail.com]

Hi sorry, My car is a 1989 BMW 750il. I will look at the vin as you instructed and will get back to you. Thanks