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Thread: Alarm Activates When LOCKING Doors after short at Trunk Lock actuator

  1. #1
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    Default Alarm Activates When LOCKING Doors after short at Trunk Lock actuator

    I caused a short when I made a connection from one of the two power wires for the trunk actuator to one of the command/signal lower voltage wires from the other connector.

    Now the alarm goes off when locking the doors.

    I think I made it worse in fumbling desperation by disconnecting what I think is the Trunk mounted level sensor (tow away sensor) and at this time the remote (three button Fob) no longer communicates with the car even after re-connecting this sensor.. maybe an initialization block?

    Anyway.. I had the car scanned by a BMW trained tech who knows e34 540's he used to do the short block swaps way back.

    He suggested I may have damaged an actuator .
    The locks lock then open then lock again as the alarm is triggered.


    There was no initialization block when he scanned it.

    I was unaware an actuator could be damaged in a way that would cause it to trigger the alarm . I thought their failure just caused the system to kick back and you have to re-lock.

    Just wanted to see if anyone had a brainstorm with this.. I have a copy of the BMW EWS but haven't looked at it much as reading schematics is a skill I have yet to grasp.

    I am assuming the shorting which occurred would need to be traced to the next nearest component first which could in any way trigger the alarm.


    anyway I hear or heard before disconnecting that trunk mounted level sensor the clicking in both the back seat locking unit and the front left A pillar/foot well mounted Alarm module..

    I am willing to replace actuators and whatever modules may have been damaged yet I am hoping I might proceed with better understanding which could help avoid unnecessary expenses

    Its been a rough few weeks here.. Hope everyone is doing well.
    Last edited by Jehu; 05-15-2016 at 03:22 PM.
    1995 540i Manual build 1/95

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    As I understand it, the GM senses the position of the locks via the switches on the actuator. So if the boot lock actuator is damaged, that may be causing the problem. Not sure about your car but I think the part number on mine is 8353000. May be worth swapping one from a breakers and checking what signals the GM is getting from it.
    Oct '00 E46 330i. Feb '92 525i (departed)

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    Quote Originally Posted by whiskychaser View Post
    As I understand it, the GM senses the position of the locks via the switches on the actuator. So if the boot lock actuator is damaged, that may be causing the problem. Not sure about your car but I think the part number on mine is 8353000. May be worth swapping one from a breakers and checking what signals the GM is getting from it.
    While the Trunk Lock Actuator was disconnected completely when I did this and the doors did lock properly via the remote key before the shorting which to me rules out a faulty Trunk Actuator (remember it did lock my doors precipitating this bother) I gather if your logic is accurate damage was done to a door actuator .

    So you're sure the method by which the Alarm System receives door locking condition is triggered within the actuator?
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    Last edited by Jehu; 05-16-2016 at 12:43 PM.
    1995 540i Manual build 1/95

  4. #4
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    Well, you can't have shorted out the boot actuator if it wasn't fitted :-) But this is how I understand central locking works: The boot and front door switches send open/close signals the GM. The GM then signals the relay module which powers up the motors to open/lock the doors. The GM monitors actuator switch positions so it knows if the boot lid or a door is open or closed. The alarm module monitors the central locking and AFIK, you can't set the alarm without the car being double locked. That may sound like so much gibberish but if you check out section 10 in the file below, you will see what I mean. It is in German but includes diagrams for the GM and switches:
    http://twrite.org/shogunnew/files/ED...lectronics.pdf
    Oct '00 E46 330i. Feb '92 525i (departed)

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    Quote Originally Posted by whiskychaser View Post
    Well, you can't have shorted out the boot actuator if it wasn't fitted :-) But this is how I understand central locking works: The boot and front door switches send open/close signals the GM. The GM then signals the relay module which powers up the motors to open/lock the doors. The GM monitors actuator switch positions so it knows if the boot lid or a door is open or closed. The alarm module monitors the central locking and AFIK, you can't set the alarm without the car being double locked. That may sound like so much gibberish but if you check out section 10 in the file below, you will see what I mean. It is in German but includes diagrams for the GM and switches:
    http://twrite.org/shogunnew/files/ED...lectronics.pdf

    Ok the locks do double lock if I lock either of the front doors with either the door button or key blade in the tumbler.

    For now I'll ignore the remote system . It was working until I unplugged that leveling sensor so I am assuming that caused a block to the remote but it was functioning fine right along .

    Is it logical to look at one of the door actuators now due to receiving a 12V surge from my jumpering and is now letting a signal through to the alarm when entering the LOCKED position?

    Without yet properly understanding the circuitry of these door actuators that seems to make some sense.

    I am guessing the very nearest component to the wire I jumpered would be the first one to replace.

    Well I'll grab a couple of cheap-o chinese actuators off ebay and see where that gets me beyond $50 poorer..

    I very much appreciate your taking some time to help em think this through.

    All the BMW indy shops round here are booked for weeks and the one I did have scan the car found nothing clearly at fault
    1995 540i Manual build 1/95

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    I'd hang fire with buying anything. Getting to the front door actuators would be a right PITA and if both doors double lock and unlock, it may be a fruitless exercise. My concern would be possible damage to the GM. I know it has a power protection relay but I don't think it is intended for this kind of problem :-) I think you mentioned it is a 540i but maybe confirm build year/month? If you are in the US, you may have the Alpine system but perhaps confirm that too? That way we will all be looking at the same diagrams :-)
    Oct '00 E46 330i. Feb '92 525i (departed)

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    Not an Alpine system build is 1/95.

    I ordered for $20 a rear actuator thinking this could be nearest the trunk in series and I seem to recall once or twice while trying to get an idea what was going on that one of the rear doors was not locking along;

    I have another 540 accessible so maybe I'll grab the GM and RM from that and see if it works..

    I am sort of still thinking about the DWA module and reading this part requires the dealership reprogramming under certain circumstances

    I may bring that along from my other 540 too and then with all these items new I can see about having the dealer or someone with the necessary software to zap the unit to re connect with the key.

    As for the door panels. I have replaced an actuator in the front passenger door before and the day before I screwed up I replaced the driver's door brake so had that panel off.

    Its not always as bad doing the job as it is contemplating it. Especially when here my alternative is not being able to easily lock the car.

    I use it to transport expensive IV drugs for a pharmacy so it could get really annoying if I find I need to lock the car with boxes of stuff in the back seat and need to disconnect the battery ..
    1995 540i Manual build 1/95

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    My apologies. I missed that you have got your model details on the footer :-)

    I don't know which DWA module you have but AFIK 8355139 is the alarm and ultrasonic control module. It also controls the horn and has an external fuse. Not sure if the horn would function if that fuse were blown but it might be worth a look
    Oct '00 E46 330i. Feb '92 525i (departed)

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    Quote Originally Posted by whiskychaser View Post
    My apologies. I missed that you have got your model details on the footer :-) I don't know which DWA module you have but AFIK 8355139 is the alarm and ultrasonic control module. It also controls the horn and has an external fuse. Not sure if the horn would function if that fuse were blown but it might be worth a look
    the horn will be silent if I pull the fuse on this unit but the lights still flash and since losing communication between the remote and the car as I mentioned they flash for the full several minutes.. so I just don't bother since pulling the fuse loses me the OBC function.
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    1995 540i Manual build 1/95

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    That's the one :-) As you say, it contains the horn relay and powers the OBC. If it is DWA4 I think you can only disarm the alarm with the remote. Have you tried to turn it off using the emergency procedure or resync the key? You don't need to code the module for either of those
    Oct '00 E46 330i. Feb '92 525i (departed)

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