Sterio is not not working since the battery died. LCD display reads "CO:DE". on 1991 BMW 325i

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I left my lights on my 1991 325i and had to call AAA. Since that time the radio is not functioning. It reads "CO:DE" on the display and beeps loudly when any button is pushed. How do make it work again?
(1) Answer
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The only way to make the radio work again is to enter the anti-theft code. It is usually located on a card that came with your owners manual. If you don't have that you may have to visit your local BMW dealer, and be prepared to prove you own the car and radio. Also you may try any local car stereo installers, they might be able to help you out.
Thanks! I don't have the manual - so I guess I'll go down to the nearest BMW dealer and try to convince them I own my car.