Thoughts on a combination of faults

A

a340driver

Member
Hi it's been a while since I posted as the car's been working great for the last few years.

But today I got into my Z4M today and noticed the display for the stereo didn't come up when I put the ignition on. Then after starting the car normally the roof wouldn't go down. I tried switching it off and on but both faults remained.

During the drive I noticed that the Auto headlights were permanently on and the auto door lock didn't lock. Windows, wipers all perfectly fine.

I've been having an issue with the car thinking that it's unlocked when the alarm in on (locked with the remote). A rapid beep beep beep. So I've just been locking it with the key.

It's going in to have any codes read on Monday but I'd like to hear I anyone has any thoughts.

From what I can see on the forum so far possible sources could be:

Battery fault . It lives in a garage on a trickle charger normally.

One of the modules on the K-Bus, possibly the GM5 module. No signs of water ingress.

Roof motor failure causing other issues. The drain holes are dry and it's kept indoors most of the time.

I understand it could be any of the above or all of them!

If anyone has experience of other similar seemingly unconnected problems ( and solutions ) it would be a help when I talk to the garage on Monday.

Many thanks!

Paul
 
Batteries throw all manner of codes when on the way out. If your battery is more than 6 or so years old replace that in the first instance and possibly save on garage bills.
 
Sounds like the battery is on it's way out. Mine went flat and when I scanned the car I had all manner or weird errors. When it did go flat, lights were randomly on and the AC was stuck blowing. All systems went a bit crazy.
 
When the battery was getting tired in my previous Z4 I kept getting an amber EML with fault codes for post-cat 02 sensors. They got cleared but came back, then during the 2nd diagnostic session the battery died. Once the new battery was in and codes cleared they never came back.

When my battery went flat in my current one I started it with a jumper pack and the trifecta of amber lights appeared. I took the car to Ross at RBM who cleared them after resetting the steering angle sensor.

BMWs of this era seem prone to throwing all sorts of random lights and codes if the battery is dying.
 
As I understand it the problem is that if they get discharged beyond a certain point they will never hold a full charge again whatever age they are.

At least a battery is cheaper than most electrical issues, and new ones don't need coding on our cars!
 
Well the new battery (replaced under warranty as it was 2 years old on a 3 year warranty) didn't solve it.`

Took it back in and they realised the bonnet catch was causing the problem (They didn't check the codes first time as per my suggestion but it got me a new free battery (old one down to 35% over the 2 years)).

They just disconnected the bonnet sensor and the car now thinks it's properly locked. I could buy a new bonnet sensor but who is going to try and break into a 19 year old convertible via the bonnet?

Result!
 
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