Hazard lights won’t stop flashing after disconnecting/reconnecting battery (E32 730i)

[MatE32]

Hi everyone,


Quick introduction since this is my first post here : France based owner of a 1993 E32 730i, acquired in 2018 and with current mileage of 172’000 km. Just love it.


Writing today with respect to a strange behavior observed two weeks ago after disconnecting and reconnecting the battery negative cable : the hazard lights went on at reconnection and nothing will stop them from flashing.


Disconnecting and reconnecting the battery is the only I did to « trigger » this behavior (I was planning to replace a component but had to postpone this).


I found a thread on a similar issue, saying that driving the car over a short distance should stop the hazard lights from flashing, but doing so did not change anything in my case.


Sometimes, with engine running and the hood open (vehicle stopped), they stop flashing suddenly. And they flash again when closing the hood. Same happened with the trunk. Quite crazy...


I tried to disconnect the battery again and reconnect it but this had no effect.


Note that the hazard lights keep flashing even when I turn off the engine and remove the key.


The first (dirty) solution I found was to remove the appropriate fuse. This at least avoids battery discharge when not using the car. When driving however, I can’t use the turning signals, which is quite bad.


Dealing with the fuse, I noticed some sparks when putting it back in place, during my multiple attempts to understand the issue. Eventually the fuse fused.


Unexplained side effect : my two low-beam headlight bulbs died in the operation (the related fuses are ok though). Not a big deal but it puzzles me a little bit more.


Further reading pointed me to the crash control module relay (N17). Among other things, this module is supposed to put the hazard lights on when a crash is detected.


So I removed this relay and put a brand new fuse in replacement of the burnt one.


At this point : the hazard lights are not flashing anymore and I can use the turning signals properly. But the crash control module is inactive and I can’t use the hazard lights when driving (pushing the hazard warning button has not effect, as expected I guess since I removed the relay).


I inspected the relay after removing its cap : it looks in good shape but I’m not an expert.

Therefore I wonder : should I replace the relay ? Or perform other tests to troubleshoot the issue ?


Any feedback or suggestion would be really welcome at this stage.


Thanks !

[shogun]

Usual problem is a defective crash control relay https://www.bimmerforums.com/forum/s...on-by-themself
http://www.bimmerboard.com/forums/posts/410301/
02/87 model module location http://www.bimmerboard.com/forums/posts/682764
here is the info pic how to by-pass the relay with 2 wire bridges for testing
http://forums.bimmerforums.com/forum...m-switch-issue
https://www.bimmerforums.com/forum/s...-sunroof-motor

The headlight low beams have each one fuse, check both of them. Also check the LKM light control module, here I posted a pic and info from 2010 http://www.bimmerboard.com/forums/posts/847563/

[MatE32]

Thank you shogun.

I ordered another crash control relay and put it in place of the original one : same problem, the hazard won't stop flashing.

Regarding the low beams, I checked the two fuses and the two bulbs : they are all working properly. As for the LKM, it doesn't look bad to me :

LKM_01.jpgLKM_04.jpgLKM_05.jpg

Any guess ?

Thanks

[Timm]

I used to have exactly the same behaviour on my 730i - the only way to stop them was to use the remote to lock and then unlock the car. I guess you don't have a remote?

[MatE32]

Thanks for the tip Timm.

I have a remote but never used it ; I'll try to find it and do as you suggest.

In your case, does it work only with the remote or with the key as well ?

[Timm]

Just the remote as far as I remember - but that was in 2006!