I have purchased this car from my friend who had it break down on him in the middle of nowhere. Car is a 98 Mercedes E Class 320. Belonged to a friend of mine who has now sold it to me. Car is located approximately 200 miles from dealer ($700 to tow it there) and the problem started when he stopped to buy gas. Car was running fine. He turned car off, gassed up and when he got back in car the electronic key won't turn. It is also not working on the doors. He used the manual key to unlock the doors. I am told that if the battery in the car is dead (he says it is not) or if the battery in the electronic key has died, that this can cause this problem. I also was told to try to boost it and see if the key turns. New electronic key is nearly $300 and I can order it but I would like to know if there are any other solutions prior to driving out there (6 hours there and back) for nothing.

Here are tghe instructions on how to jump the battery
The battery is located under the rear seat cushion on the drivers side - lift the seat base out (or fold the seat base up if an estate model) to access the battery.
Connect the jump leads directly to the battery terminals (Positive to red and Negative to black) - positive to positive from your other vehicle & negative to negative.

Run the engine on the vehicle you are jumping from & try to start your E class. You may need to run for a while first if the battery is very flat to get some charge into the battery before starting.
If the battery is completely dead then you may not be able to jump it & the battery would need to be repla Here are tghe instructions on how to jump the battery The battery is located under the rear seat cushion on the drivers side - lift the seat base out (or fold the seat base up if an estate model) to access the battery. Connect the jump leads directly to the battery terminals (Positive to red and Negative to black) - positive to positive from your other vehicle & negative to negative. Run the engine on the vehicle you are jumping from & try to start your E class. You may need to run for a while first if the battery is very flat to get some charge into the battery before starting. If the battery is completely dead then you may not be able to jump it & the battery would need to be repla

If jumping the battery doesn't do it then you are going to need the dealer (or a qualified shop) to scan the system for fault codes, check locally for a shop that can service the Mercedes line of cars, the dealer is not the only place that will have the correct system scanner. If jumping the battery doesn't do it then you are going to need the dealer (or a qualified shop) to scan the system for fault codes, check locally for a shop that can service the Mercedes line of cars, the dealer is not the only place that will have the correct system scanner.

It is unlikely the battery in the remote is defective, they don't just faill like this, but take it out and replace anyway, it should be a #CR2032 Button Battery, they are available at almost any store like CVS or Walgreens, Radio Shack of course will also have the required battery. It is unlikely the battery in the remote is defective, they don't just faill like this, but take it out and replace anyway, it should be a #CR2032 Button Battery, they are available at almost any store like CVS or Walgreens, Radio Shack of course will also have the required battery.

Thanks for you incredibly detailed explanation. I now feel like I have a much better handle on how to proceed with the hands on diagnosis. I will let you know how it works out. Thanks for you incredibly detailed explanation. I now feel like I have a much better handle on how to proceed with the hands on diagnosis. I will let you know how it works out.