2018 BMW 1 Series rear lights coming on by themselves when

[Stanny1970]

Hi all, hoping someone can help with a strange intermittent fault on my 2018 1 Series.

Both rear tail-light clusters occasionally come on by themselves when the car is switched off and locked. It’s just the rear lights—the front lights and third brake light aren’t on.

A few details:

Pressing the brake pedal makes no difference.
Unlocking and relocking with the remote, or switching the ignition on and off, clears it and everything returns to normal.
It happens with the light switch in Auto. So far, leaving it at 0/Off seems to prevent it.
I’m getting “Battery discharging when stationary” on the dashboard.
Nothing has recently been changed or fitted to the car.
Has anyone had this exact problem and managed to get it properly diagnosed and fixed? I’ve found similar reports online, but very few follow-ups confirming the cause.

Would really appreciate hearing what actually resolved it before I start paying for parts on guesswork!

Thanks,

[bodhi]

This probably counts as guesswork - but how old is the battery fitted? Is it original to the car?

Just asking as most random electrical problems on BMWs in my experience are due to a dying battery. Another big tell the battery is on the way out on a 1 Series is when you unlock the car - if not all the lights come on (headlights, tail lights, puddle lights on the door) then it's new battery time.

Some places may be able to do a battery health check for you, but if I was going to start throwing parts at a BMW with electrical issues that would be the first part to come out of the cannon.

[Stanny1970]

Hi Bodhi,
Thanks for your feedback, the car has the original battery and this was going to be my first thought. I ran a trickle charge on it overnight as it was at 25% charged.
The following day I didn’t have any issues, but didn’t drive the car as I wanted to test it over 24hrs, the following day it was back to 25%?!

I’ve driven it today and it’s been fine but again the battery discharge warning was on the car when I started the car.

I’m going to replace the battery over the weekend but concerned I’ve read the car has to be programmed after a battery replacement? Would this be correct?

Thanks again for responding

[bodhi]

Stanny1970 said:

Hi Bodhi,
Thanks for your feedback, the car has the original battery and this was going to be my first thought. I ran a trickle charge on it overnight as it was at 25% charged.
The following day I didn t have any issues, but didn t drive the car as I wanted to test it over 24hrs, the following day it was back to 25%?!

I ve driven it today and it s been fine but again the battery discharge warning was on the car when I started the car.

I m going to replace the battery over the weekend but concerned I ve read the car has to be programmed after a battery replacement? Would this be correct?

Thanks again for responding

That does sound like the battery is on it's last legs - BMWs wlll do all kinds of strange things when struggling for juice - mine was resetting the clocks and mpg counter every other time I started it - new battery and it's fine.

You will need the new battery coded - it can be done with tools like Bimmercode or Carly - or if you don't fancy it Halfords will do it for you as part of their fitting service. In fact I'm pretty sure the AA will if it has to be fitted by the roadside.

[Stanny1970]

Thanks Bodhi, I’ve got bummer, so give it a go this weekend