Peake Code 77 - Motorized Throttle Valve (MDK) mechanically stuck.

2000 328i with 100k miles stalled on the freeway yesterday. Car cranks but will not run so had it towed home. No CEL but got peake fault code 77 - Motorized Throttle Valve (MDK) mechanically stuck. Is this the culprit and what is MDK? Bentley manual says MDK refer to Throttle. BTW, the car started fine and run smooth today but I’m afraid will stall again. Appreciate any suggestions. -Peter