CLS 55 amg issue with central locking.

[MilesMurphy]

Hi Guys,

I noticed the key battery was getting low as i had to get closer to unlock the car. I replaced the battery and now I cant unlock the car with the remote. So I thought I'd try the spare key, again no joy. swapped the batteries around and again no joy. I've checked the fuses and they are all ok. I can get in the car and start the engine with both keys. But now I cant immobilise the engine and i have to lock the car manually as the boot locking system can see the key plus the keyless start is saying "no key detected"

Tried to sync the keys but that did nothing

Help!

 

[Uncle Benz]

Are you sure you have fitted the batteries correctly? If you hold down one of the buttons can you see a red LED flash on the key? The ignition uses a different method, and will operate even with no battery fitted.

 

[MilesMurphy]

replace batteries 2025 exactly how it was when i removed it. double checked with 2nd key. then switch batteries in case 1 fob was broken. non of this resolved the issue.
I have been reading that it could be the antenna amp that gone. I have got a D302 - Cable to GPS antenna has short circuit. but where as before i could stand at a distance and lock the car. the other day i was 5cm from the windows to lock it. hence why i thought it was the battery. but now could be the antenna or the amp.

 

[Uncle Benz]

If you can access the amp check for 12v on the red and yellow wire. It's common on the w211 for the wire to break between the rear SAM and the amp, but I haven't seen this fault on a CLS. They are built on a similar platform though.

 

[MilesMurphy]

ok I'll have a look.
could just be a fault with the antenna as the gps has lost its location and amps on the left and right c pillar are connected to the antenna?

 

[MilesMurphy]

ok, I checked the key fob again and noticed the the batteries had a very thin layer of glue on them from a "don't let children swallow" sticky label. Gave both batteries a good clean and all started working.

 

[mattkh]

Well done.
Thanks for the feedback.