# 95 740il, Unlocking the OBC? & annoying message "lights"



## Ds74 0il (Dec 8, 2009)

Heard alot about unlocking the OBC but have been unable to perform it correctly! I would like to check things like my voltage (as I believe my alternator is draining my battery), i have not been able to bring up anymore options when I go to the OBC.

- also, I get two warnings when I start(when it used to start) my car "check rear lights" and "check lic plate lights" The license plate lights are a bit dim and I plan on replacing them soon, but the rear lights look ok to me? Could this be a more insidious problem with the wiring or should I just replace the lights? (anything to take off the notice!)


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## balance (Feb 13, 2009)

I think everyone who owns an E38 should check out www.E38.org, in the link titled "OBC unlocking" it will tell you in detail how to unlock it and and what each test is. As far as the warning lights, it's possible that with the low voltage, that the computer is going crazy and giving out false alarms, so I would get the battery checked out. It's impossible for the alternator to kill a battery unless it has stopped putting out power or the power wire is grounded or loose, your problem could just be a bad battery so I'd get that checked out first.

Engine off voltage should be around 12.6v
Engine on voltage should be between 13.9v - 14.4v


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## Ds74 0il (Dec 8, 2009)

sweet, i had been to the e38.org a few times before but must have skimmed past it, found it now and I think I can handle it. Thank you!!
as for the battery, I know its bad because the alarm and door locks wont even work and everything electronic is progressively getting dimmer or turned off! Is the e38 just such a beast that it would need a new battery every 7-8 months or should I check for loose wiring from the alternator?


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## balance (Feb 13, 2009)

I didn't know you changed the battery 8 months ago so that's probably not the problem. Then again I installed a brand new battery in a car before that had a dead cell. If you think that it's the alternator, start the car and check the voltage on the unlocked OBC and see if it's in the right range. I'm pretty sure that most autopart stores will check the charging systems on cars for free so you can take it there if you want, but make sure the battery is recharged first because a low battery can throw off an alternator test.


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## CodyItaliano (Feb 19, 2009)

just to be clear, an alternator can actually "kill" a battery. that is if its reluctor is malfunctioning. which it would be putting out alternating current instead of direct current. that can result in a dead cell, which usually when you test a battery that has experienced this situation will only have about 10 volts. this is the most common thing i see with a bad alternator that has not been discovered soon enough. anyways hope you get your electrical issues fixed, i know they are a headache.


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## balance (Feb 13, 2009)

Wow, I didn't know that Cody. If there was a bad alternator and battery in the same car I always assumed that the low battery killed the regulator on the alternator.


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## Ds74 0il (Dec 8, 2009)

Thanks Cody, I had heard the same thing from a few other people- new alternator & battery it is any idea what labor would be for both? no point in doing the battery myself after the alternator gets put in if they should both be tested once in....:dunno:


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## balance (Feb 13, 2009)

I would ask whoever checked out your car to give you an estimate, and if you didn't get it checked out then I would do that first. What if it's not the alternator that's killing your battery?


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## CodyItaliano (Feb 19, 2009)

do get the battery charged and tested, also get the alternator tested on and possibly off the car if you can. best bet is to test the battery off the car. the alternator can be tested on the car. as far as labor, its a bimmer. but thats no excuse, it should be about a $200 job, i know the alternator isnt that hard to take out. neither is the battery. 

BTW, how many miles are on your E38?


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## Ds74 0il (Dec 8, 2009)

I have 140k on mine. 
it seemed like such a great deal that i wasnt going to pass up the purchase....but now, im a bit concerned. it's always something, from little things like the "check rear lights" & "check lic plate lights", a "trans failsafe prog" (only once, and I think it's because of the fuel line cleaner i put in it,lol), up to this "My car is completely dead" issue. not to mention that 2nd gear shifts just a little funny, but I heard it a "sealed for life tranny" and now im afraid to get a tranny fluid flush else it creates more problems!
-with all that said though I really cant wait to start accessorizing it,lol, and it does feel awesome to drive


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