I have read several things here but did not find the answer to my issue. I have a 1997 E320 that has power locks. I can no longer lock the car with the fob but can manually unlock the car from the truck. I only have one key hole type on the passenger door and when I use that the car locks but I can't get anything unlocked! Help.

Simple questions first: Did you replace the battery in the key fob?

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

On a one button remote, hold the button down while looking at the red square on the edge of the key fob. If the battery is good, this square will blink.

To sync the remote to the car, press the remote button twice while aiming it at the car then insert the key in the ignition and turn it to run.

Remember, the remote on these cars is a infra red light beam like a TV remote. You can also aim it into a video camera and look for flashing. Test your camera with a TV remote as some cameras are not IR sensitive.