I have a 2001 e320 with 103000 miles

ESP lighted up, engine running but unable to accelerate. Display Visit Workshop, the code is P0120.
It starts fine but runs at 1200 rpm and after pressing the accelerator goes to a maximum of 1600 rpm while parked.
When I drive it will go up to 12 miles per hour with the pedal to the floor.

Please any help would be appreciated

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