Under thr right rear trim panel (opposite spare tire) there is a second part to radio/stereo system. There is a 5a fuse in this radio section & it is probaly blown. "E2" means that rear half isn't responding to commands from the front.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V