BMW OBC Anti-Theft Code E23, E24, E28, E30, E32, E34, E36
This answer is applicable for many BMWs in addition to the one listed below.
car year: 1988
car model: 325i Convertible
I just got my second BMW. It is a 325i 1988 convertible. This afternoon I went to a place to have it cleaned inside, but I do not know what happened. When I try to turn it on, the horn starts beeping and the main computer ask for a code (?) and the car does not start. Without starting the car, I turn on the main switch and the computer ask for a code. If I type any combination of numbers the horn starts beeping again for 30 seconds, and then stops, waiting for another code. What should I do? I cannot use my car.
The ’80s and ’90s BMW models (E23, E24, E28, E30, E32, E34, E36) that have the separate On Board Computer units (OBC), such as your E30 chassis (3 series 84-91), have an anti-theft feature available within the OBC. If this feature is activated, the pre-set 4-digit code must be input. When activated, the starter will turn, but the engine will not start. After 3-attempts, the horn will sound for 30-seconds.
It’s likely that the people doing the cleaning, accidentally activated the anti-theft by pushing the OBC CODE button while the key was in the #1 position (perhaps listening to the radio). They may have just been lucky enough to push the buttons in the sequence that ended up storing a code and activating the system.
The owner’s manual for your 325ic gives the sequence and instruction for activating, using and de-activating the system, but there is no mention of what to do in case you “forget” the code you input. However, the owner’s manual for a later model E34 chassis (5 series 89-96) does mention an emergency procedure for the system (which is similar to your 325ic). So, give it a try. If this does not work (remember, it is for a different model), try just disconnection the battery for 15-minutes, or so. If this also does not work, we can tell you how to by-pass the system, by cutting and splicing the wires for the anti-theft module.
EMERGENCY START PROCEDURE – IF CODE HAS BEEN LOST:
* Disconnect battery for 5 minutes, or more.
* Reconnect battery.
* Turn ignition key to position 1 (alarm should sound).
* A time display will appear and run down to zero (for 15 minutes).
* After 15 minutes, the engine can be started.
During the waiting period of 15 minutes, the code can be re-entered.
* Press CODE button.
* Input desired code.
* Press the S/R button.
* Start the engine.