siegfried979

Hi all,
Few days ago had a window retinting done at the shop. Drove back home and locked car for the day with no problems.
Next day key fob remote buttons not working. Saw that batteries were not working (red dot light not showing with button press), so replaced batteries (for some reason old batteries were 2036 + 2016) with 2x 2025. Red light is working now but none of the key fob buttons are responding (lock/unlock/panic/trunk).
**UPDATE below

What I've checked so far:

1. I had just had a window retinting the day before, so I wondered if something happened then, but I was able to drive it back home and lock the doors via remote that night. Called up the shop today and they said they don't use metallic tint so might not be signal interference issue (they could also be incorrect but I'll take their word for it for now). Plus I could drive, lock and unlock my car that night. Problems started only the next day.
2. Double checked fuses: nothing blown out.
3. Red light shows along with button press on key fob after battery replacement. With a phone camera test IR still seems to be functioning.
4. I can use physical key to unlock doors. Key fob can still start the car, but usually there's a splash screen with the dashboard LED screen when inserting into ignition (position 0/without turning). This time, nothing shows until key is in position 1/2.
5. Radio functions normally so might not be an antenna problem.
6. **UPDATE: The remote actually works when I point it anywhere from 0~.5 ft. away from the little IR(?) receiver next to the handle of the driver's side door. Anywhere outside of that range won't work. Also a bit finicky. It works better at night but I have to try and angle it correctly in the day.
7. **UPDATE2: I bought a new key fob from Mercedes. It still can't unlock the car via radio frequency. However, IR blaster works perfectly. I guess there might be something wrong with the antenna.

Trying to narrow down what's going on. Any ideas?

MIA2PSP

Turn key to position 2 then back to position 0 and remove it.
2. With in 60 sec. push the lock button and lift gate button at the same time for 15 sec.
3. Press any remote control button twice to activate the system.
Second procedure:
1. Turn key to pos.2 and back to pos. 0 and remove it.
2. with in 60 sec. press and hold the lock all button.
3. While the lock all button is depressed, press unlock button 5 consecutive times.
4. Press any RADIO remote button to activate the system.

MIA2PSP

I've bought as many 2036 and 2025 batteries for remotes/fobs that were weak or dead out of the package as I have that were good. Try that resync procedure and if no help go buy new batteries.
FYI When the fob is inserted in the ignition it draws the power for the ECM (handshake) function from the vehicle not the key fob batteries. So if it's starting with the fob but all dash messages etc are not activating that could be because some of the signal required for message center functions could come from the battery powered chip in the remote. Indicating obviously low power or dead remote batteries.

siegfried979

I just replaced with newly bought batteries (2032+2025) and unfortunately no changes. I tried the procedures listed but nothing seemed to happen.

I'm erring towards it not being a problem with the car since radio, fuses all seem to be fine. I wonder if the key fob itself is somehow just very weak in general? I was actually having trouble getting the IR to work on the door handle today. Had to really prevent light from interfering with the IR blaster by covering it with my hand to get it to work. Still, it could also be that the receiver isn't in great condition either but I don't know how to check that. If RF isn't working and IR is weak, it might be a key fob issue.