After locking my Fabia and when the immobiliser kicks in, the rear lights and front side lights come on and flicker. 

Is this an immobiliser problem?

The battery went flat today after a few hours of the lights flickering. 

Could it be battery problem, key fob or something else 🤔 

Hi welcome.

 

Could be a few things and possibly more than one issue, have you only noticed this today or before, is it wet /damp where you are.

 

It won't be the car battery or remote keyfob.  You may need the help of someone with a VW appropriate scan tool and/or auto electrician.

 

You would possibly get more and better answers in the forum for a Fabia Mk2 or Mk3 depending on which yours is.

 

Skoda Fabia Mk II (2007-2014) Discussion for the Mk2 Skoda Fabia from 2007-2014. - https://www.briskoda.net/forums/forum/113-skoda-fabia-mk-ii-2007-2014/

 

Skoda Fabia Mk III (2014-2021) Discussion for the new Mk 3 Skoda Fabia from 2014/5-2021 - https://www.briskoda.net/forums/forum/298-skoda-fabia-mk-iii-2014-2021/

 

Thank you for this.

The battery is old but showing good charge.

When it happened it was cold minus 2c.

I think you are right with an auto electrician. 

There are no on board signs 

Auto-electrician preferably with a scan tool that covers the complex VW computer programs.

 

It depends on when the car battery was measured at good charge but even if it's old but provided you have not used/abused it too much too often for too long an appropriate battery charger (maintainer) could give it more life and longer life.  The cold weather (and hot weather) isn't ideal for the battery but -2 isn't extreme, lack of warnings doesn't necessarily mean the battery isn't low and doesn't need charging but if you have taken a reading at an appropriate time and it shows good charge fair enough.  But a low battery wouldn't cause the problem you have, as you put the issue has drained the battery.

 

If your car is start/stop unless it's passed that point a low battery gives the warning the battery is too low to operate that system, if you ignore this and continue draining the battery then all sorts of other warnings might light up but the engine still starts.

 

Remote keyfob also isn't so good when cold or hot, it going from a warm home to outside (or inside the car) when its very cold can lower its performance and you probably notice sooner and more if you have KESSY.  But again a low battery wouldn't cause the problem you have.

 

Posting in the appropriate forum with more information about your car may bring replies with experiences and knowledge and perhaps an answer.  A forum member with an appropriate scan tool may be able to give a scan report or point to an area that might be the cause.

 

Good luck.

 

it'd be good if you reported back the final result/solution as this might help others.