OK, I've had this issue several times, the last time was resolved with a replacement battery in the fob. Now I can press the fob and see the red light flash but no action on the locks. I can pull the key out of the fob and manually unlock the door, start the car and turn it off, exit and press lock and it does so. Could this be the #7 or 8 fuse that I've seen referenced for this problem? I can't understand how it will work sometimes and not others... either the fuse is blown and it won't work or it is good. Anybody have a go around with this one?
Cyberbach
Does this also happen with the second key fob? Does your car have the Keyless-Go option? You may want to check the battery on the key fob again.
The fuses for the central locking are 70, 80, 81, 82, 112, 126. If you have Keyless-Go it also includes the previous fuses and 37, 131. You may want to check those fuses as well.
The fuses for the central locking are 70, 80, 81, 82, 112, 126. If you have Keyless-Go it also includes the previous fuses and 37, 131. You may want to check those fuses as well.
I have yet to check the fuses because the way this is happening it's intermittent and a fuse either works or it doesn't correct? I can lock the car up after driving it and the fob works flawlessly, open, close, trunk open and close. The I go in the house for a few hours come back out and nothing... the fob lights up but nothing is actuated. I pull the key out of the fob and unlock the door... sometimes the alarm sounds, sometimes not but once I start the car the fob will work again. I'm always able to lock the car but sometimes after it sits it won't open. I only have the one key fob and an extra courtesy key.
The other thoughts are that the antenna for the central locking is having intermittent connection issues. The antenna is embedded in the rear window. Look at that and the connector and make sure there is continuity. Also, follow and check the connections to the rear window antenna amplifier module (A2/12). The shop manual says it is in the rear center of the roof. Once you find the module, it is very difficult to determine if it is faulty, unless you have a replacement available. The module looks like this on eBay: 07-13 Mercedes W221 S550 Rear Window Antenna Amp Amplifier Module 2218208489 OEM | eBay
The module then connects to the Keyless-Go module (N69/5) in the trunk, right side. Check for loose connections. See the wiring diagram below and see the photo below for the Keyless-Go module, it is in the red cloud.
You may want to still check the fuses. There are a lot and one blown fuse may handicap the system, but still make it work, but sometimes not.
![Image]()
![Image]()
The module then connects to the Keyless-Go module (N69/5) in the trunk, right side. Check for loose connections. See the wiring diagram below and see the photo below for the Keyless-Go module, it is in the red cloud.
You may want to still check the fuses. There are a lot and one blown fuse may handicap the system, but still make it work, but sometimes not.
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