Many times the transmission is reacting to the amount of torque that the engine is putting out. IF the engine isn't developing enough torque then the trans will remain in the lower gears.
Many times on the M112 like yours the air mass sensor leans out the mixture & then the engine doesn't develop enough torque.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator