I recently purchased a 2004 E320 Wagon. After I got her home I locked her up using the electronic key. The next morning the electronic key would not unlock the system so I used the metal key which set off the alarm. Changed the battery in the electronic key which did not improve things. I then decided to purchase a new key.

Initially the new key worked well, for about three cycles! The last time that I was able to make it work a warning popped up that said something about the battery but the screen changed to "take it to a service station" so I wasn't able to get all of the message.

Any help or suggestions would be deeply appreciated. Thank you in advance!

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Roc

'74 350SLC (Euro) (For Sale)
'01 CLK55
'02 Jaguar XK8
'04 E320 Wagon
'89 Ferrari Mondial T Coupe
'57 Volvo PV-444 (Vintage Racer in build) (For Sale)
'80 Mazda RX7 Enduro Race Car (For Sale)

Check the vehicle battery voltage, I've seen batteries that lose a cell and end up with a 10 V battery. This can scramble electronics.

This car might have a 2nd battery for the braking system, I'm not sure.

Many auto parts stores have a remote battery display and a tester for RF and IR remotes so it would be a good idea to see if the remote is consistent.

I'd think that there would be a way to scroll through dash error messages.

Just be thankful it starts the car!

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra