timwit

My key fob will not activate the locking system (doors and trunk) and panic alarm. Lights do not flash either. The manual key works and the interior switch for the door locks work. Key fob works fine in the ignition.
Any ideas would be most appreciated. Thank you.

bobterry99

Very likely either the key or its batteries are defective. Good batteries are indicated by a brief flash of the fob's tiny LED when the lock or unlock button are pressed. Consult your owner's manual for further information.

timwit

Thank you bobterry for your reply. I have three key fobs and all have new batteries and LED's all flash. No luck.

bobterry99

That is a critical detail absent from your initial post. I'll reply again to this thread on Saturday if your problem remains unresolved at that time.

timwit

Hi bobterry99. Problem still persists. If you have any suggestions could u kindly advise. Thx, Tim

bobterry99

When you press the "Panic" button the key transmits an RF signal to the antenna amplifier located behind the dash at the right-side "A" pillar. That signal is then relayed to the ignition switch module (EIS) via the overhead control panel and the vehicle communication network (CAN). If the EIS recognizes the signal as coming from one of the vehicle's keys, then the lights flash and the siren sounds.

Since you have three presumably good keys, I suppose the amplifier is suspect. That said, I am not a Mercedes tech, and I have never encountered this problem. It's possible that an experienced tech has seen this many times, and the problem is always the same.

A 5-ampere fuse in the rear fuse box powers the antenna amplifier. I would check that. If it is fine, then I think your next step is to employ a $300 Star Diagnosis kit to determine where the signal is being lost between the key and the EIS.