My 03 Mercedes s500 will not shift out of second and the shift display is not working

I could be mistaken.....BUT I think there's a separate computer foe the transmission.

I had the same problem with my 2003 S500 4Matic, after I wased my car's engine compartment with water hose. I took it to advance auto parts. Their computer diagnosed it & recomended to replace the Transmission sensor/ computer. Since this is very costly & needed an experienced service garage tech to work on, I took my car to a service garage. They changed several computers/ sensors & and took several days, before it got fixed finally. It cost us a lot of money as well. Before you do any of the same mistakes I made, please try the following easy & inexpensive steps & feel free to call me at 248 760 7789 anytime. 1. Cut your engine off. 2. Open your Hood & the Fuse Box, located on right/passenger side firewall, near the hood hinge. 3. Make sure your Fuse Box and all fuses are completely dry. 4. Air dry it thoroughly, if necessary. 5. Inspect to make sure that all fuses are working fine. 6. Replace any questionable fuse or fuses. 7. Fully close your fuse box and hood. 8. Start your car & carefully test drive it. Best of luck. Hopefully, this will solve your problem. Again, feel free to call me anytime at 248 760 7789.