OK so I thought I'd make my own thread about this as I think I've read every thread on every BMW forum that relates to this strange phenomenon and I still don't have a definite solution - it seems it can affect all BMW cars around the similar age to the X5. So it's time to do some testing and fault finding of my own and start to rule out all the possibles of what's causing it as it's gradually getting worse and driving me round the bend and making me not want to take the X5 out anywhere. Hopefully it will help someone in the future.

Symptoms are the hazards will come on....followed very shortly after by the interior lights coming on and very very occasionally the doors unlocking. If I don't notice this has happened it will drain the battery which obviously means that when I next to come to it it won't start - not exactly ideal. I recently removed the interior light fuse in an effort to combat the effects to stop the battery from draining so much but it didnt really help.

This strange behaviour can literally happen at any time and has happened during these times...

1. When starting the car
2. When driving the car
3. After locking the car

I installed PA Soft 1.4 on my laptop at the weekend and I found this when I scanned the body control module (ZKE)...



"Crash Sensor Activated" (other errors - mirror has never worked on the car since I've had it and I pulled the fuse for the interior lights myself)

So after doing all my research I narrowed down the possible culprits as to what could be causing it.

In order of probability I believe they are...

1. Faulty Xenon Ballast (REPLACED - NOT THIS)
2. Faulty Crash Sensor(s)
3. Faulty Body Control Module
4. Faulty Airbag Module
5. Faulty Light Control Module
6. Bad Battery (REPLACED - NOT THIS)
7. Ignition switch
8. Something else?

So starting from the top....tonight I swapped out the old original BMW ballasts for some cheap Chinese replacements. The drivers headlight had started acting up occasionally not firing up until you turned the switch on and off a couple of times which together with lots of other people saying the same thing made me think that this was number one culprit. I'd already changed the bulbs not so long ago so didn't think it would be these.

I got a pair of ballasts for £50 of eBay. Obviously they were different to the BMW ones so took a little bit of customisation to hold them in place. Zip ties to the rescue. Not overly pretty but very functional. Also I need to stick the boots back together with some superglue when I get some.

Few pics...








So with both ballasts swapped and firing up first time things were looking great and I was feeling positive!

Drove home and parked up on the drive, walked in and got a shower. Came out the shower 10 mins later walked downstairs and could see the hazards flashing through the window!! FAILURE....

So next thing on the list are the crash sensors - I'll probably replace all of them at once to make sure they've all been done once I've figured out where they all are.

If anyone has any similar experiences I'm all ears as to how you managed to resolve it!

To be continued.......

* UPDATE * - Added MRS module (air bag) & LCM (light control module) as a possible culprits too. I'll scan them tonight see if anything is picked up.