Car won't start - immobiliser
 

My e220 won't start, i'm not sure if its the immobiliser or the actual key fob battery thats dead but the car was left for 3 weeks and which meant battery died but now it wont start and the central locking doesnt work. Can anyone help

use the little key and manually lock/unlock your doors. and hook the battery up to a jumper box or a charger.

the key fob has a red light that blinks when u push it, it also tells u that ur battery is good. if it doesnt blink, it means its time for a new keyfob battery

You do not need batteries in the key fob at all to start the car. Looks like your main battery is dead but you should notice that easily from lights etc.