1998 E320 Key remote
 

I have a problem with my 98' E320. The key remote when insterted into the vehicle does not turn the on(the lithium batteries have been changedd) However, the spare key which does not have the remote function, turns the car on. What can the problem be and how may it be resolved.

Thanks in advance!

The battery in the key is used to power the signal used to lock/unlock the doors. It has nothing to do with the start sequence; that communication occurs via a transducer in the key.

Check the lights beneath the RR mirror and check to see if they are flashing (together, or alternating) using the bad key.