BMW Immoboliser over-ride?

JohnCleary

Right, here's the situation.

Friend has a 520i (1995) that's been lying up for a while, so he took out the battery. There was a Cobra alarm installed in it, and the factory immoboliser disabled.

Now we just removed the cobra alarm because we were having trouble with it, but since we put in the new battery, my guess is that the factory Immoboliser has re-activated.

The problem start's here. He has 2 keys. One of them has a single button for the central locking, and i'm guessing to disable the immoboliser (Transponder maybe?). This is broken, absolutily smashed to bits (He sat on it) but it never bothered him because he used to just disable the Cobra alarm with the fob, stick the key in the ignition and off he went.

I had a Rover before that had an emergency immoboliser over-ride. I had a code and the code was input using turn's of the key in the driver's door.

Does such a system exist for the BMW immoboliser, and if so, how is the code input? He does not have any code, but before he potentially embarrasses himself up at the BMW dealers when asking for a code, can anyone confirm the immoboliser over-ride procedure?

colm_mcm

I think the old type 5 series has a button underneath the car that a code has to be tapped in with. I knew a guy with a 1991 520i and he had to do this a few times. not sure if this applies to your friends car though.

Mr.Diagnostic

Hi,

There is no override for the factory system. It is a transponder based system so the key button has no effect on it but the central locking does. If the car has an on board computer that could be the cause. The factory system sometimes needs to be reset after the battery has been disconnected.
Is it possible that you did not join whatever circuit was bypassed by the aftermarket alarm when you removed it?

JohnCleary

Thanks for the replies.

The reason we removed the Cobra alarm (Just unplugged) was because we couldnt get the fob and the alarm to re-sync. I now feel that there was an immoboliser built into the Cobra system (I was hoping it was just an alarm) and unplugging cut the line, I guess I may have to re-plug it and try to re-sync the fob and Cobra system.

There is an on-board computer (With the service interval lights), could this have anything to do with it?

Mr.Diagnostic

The Cobra Alarm will have the facility to break a circuit so as to achieve immobilisation. Unplugging it will leave this circuit open. If you can ID the two wires involved then all you need do is short these out. DO NOT short anything unless you know what it is. Often the immo circuit is two wires of the same colour.
You need to eliminate the alarm as a problem before you look further. Most aftermarket alarms like the cobra will default to the set state after a power reset. It may be worth a try to disconnect the battery, switch the ignition on then reconnect the battery. Sometimes this will stop the alarm from setting as it is designed to not set with ign on.

JohnCleary

Mr.Diagnostic wrote:

The Cobra Alarm will have the facility to break a circuit so as to achieve immobilisation. Unplugging it will leave this circuit open. If you can ID the two wires involved then all you need do is short these out. DO NOT short anything unless you know what it is. Often the immo circuit is two wires of the same colour.
You need to eliminate the alarm as a problem before you look further. Most aftermarket alarms like the cobra will default to the set state after a power reset. It may be worth a try to disconnect the battery, switch the ignition on then reconnect the battery. Sometimes this will stop the alarm from setting as it is designed to not set with ign on.

Thanks for that, the problem we're having is that as soon we we connect the battery BEEP BEEP BEEP the alarm goes off... neighbours not too happy! And then the frickin fob won't sync with the alarm, even after following step's from Cobra's website

maidhc

Fob battery dead?

JohnCleary

maidhc wrote:

Fob battery dead?

Nope, LED is lighting up on the fob

Even tried removing the fob battery for 10 seconds, and followed the Cobra instructions to re-sync, sitll nothing