Q: Transmission on 2007 Mercedes-Benz S550

i have had code 0420 come up for quite a while now and i suspect a leaking intake manifold gasket. lately the trans as been going into limp mode and i was wondering if the continued presence of coolant leak into yhe intake would cause trans to go in limp mode. another question is if i fix coolant leak do i need to replace catalyctic converter?

When accelerating from a stopping point the car jerks. I can hear the clutch changing gears, it has a clicking sound. When I come to a stop it sounds like it wants to cut off. While driving there is a loud humming noise. When I start the car it sometimes may cut off then I restart it and it finally catches. What could be the issue? How long have you had this problem? A few months

It will not turn on or nothing