Tips of BMW CAS key programming and comfort access

Here are all tips about BMW CAS key programming and comfort access. Wish this helps someone.


What is comfort access system?

The comfort access system puts an end to searching for car keys in your handbag or pockets. Simply approach your BMW, open the door and press the Start button. Your unique key is recognised remotely by the comfort access sensors.


How to enable/disable keys and comfort access ?

The two key thing applies to comfort access. (Only two keys at a time can trigger the comfort access system, all other keys act like normal keys.)
You could check the VIN on the CAS to see if it matches the vehicle but even that’s not 100% certain without doing some very advanced digging.
Rheingold can enable/disable keys but only the preprogrammed transponders in the CAS. It can’t make your key work if the transponder in your key isn’t in the eeprom of the CAS.
There’s also a function for reading which key number is in the slot on the dash. If it comes back as unknown then your CAS isn’t original.

Will Xhorse VVDI2 do BMW CAS4+ key?

How to program the CAS to match the key?

There are tools that can do it. But you’re going to spend 5-10k for them. Much cheaper to have the dealer sort it out.


If you want to avoid dealer i suggest you either:
1. Buy used CAS+DME+KEY set and have someone with correct tools program everything so it matches ur car. In fact a like for like set will be a straight plugin in and drive away as CAS AND DME are already synced. However there will be VIN MILEAGE and other mismatches.
2. Buy something like BMW multi tool and a VIRGIN key and program it yourself. When done just sell the tool on professional sites like to recoup cost.


Where can I buy a Virgin key?

Check China auto software vendors for virgin keys and transponders, they usually have them. Usually fine. The plastic feels a bit cheaper but you can just swap it over with a used case from
Essentially you need to get the ISN key from your CAS. BMW MULTI TOOL v7.7 does this automatically. You could get an eeprom dump from the CAS any other way you like and then buy a cheap HITAG 2 KEY programmer and program the key that way. This will be slightly cheaper.


All BMW CAS key programming requires ISN functions?

You need to match the ISN between CAS and DME. Changing VIN in DME is not enough to make it works.


In E Series, For key programming, all keys lost, also ISN is required to make the key in this case (encrypted CAS3+, models 2008 and up)

In F series, F01, early F010 are easy, any tool can do it. you must consider the CAS4+ (EWS5), started in 2013 F010, F020,…, this type requires also ISN reading from DME to make a key.


In short: key programming for BMW models 2008 and up requires ISN functions, you must find the proper tool (VVDI2 bmw) who can read ISN.

If your target is 2007 and below, any cheap tool can do this job for you.