318is check engine electrical

[newscam]

I have a 92 318is with the check engine light coming on. It comes on at speed on the highway and when I reve the engine it goes off. I punched the gas pedal 5 times while holding down the odometer button and got the trouble code 1231. I did an internet serch and found this means battery voltage low. My battery is good. Any ideas? Could it be a bad alternator or voltage regulator. Another symptom is my head lights. They pulse when I am standing still at stop lights. Any help in this diagnosisi would be greatly appreciated!!

Thanx--newscam

[fun2drive]

You need to measure a few things. Measure the voltage at idle going into the battery. Measure the voltage at a fast idle 2000 rpms.
They way most regulators work is once you start the car the regulator will gradually ramp up to around 14.5 V max to 13.7V min values.
If you are not getting at least 12.6-7V at idle once the car has been idling a while and your 2000 rpm measure is low too then most likely you have a bad voltage regulator.
good news is that the regulator is on the back of the alternator on the left side standing behind the alternator looking forward.
I am fairly sure it is a Bosch part so you should be able to replace this assuming the alternator is good.

[fun2drive]

Here is a web site on Pelican Parts that shows your regulator.
http://www.pelicanparts.com/bmw/catalog/shopcart/BE36/POR_BE36_ELchrg_pg1.htm#item4
As you can see it is mostly removing a couple nuts on the back and removing the old and installing the new...

[newscam]

Thanks fun2drive! Sice it is now Suday I will check it today! If it is not the regulator could it be the alternator? If i got a new alternator, does it come with a votage regulator already on it. Any info is greatly appreciated. Thanks again.

newscam