That valve clicks with the key on, engine off? That valve has a constant 12V with the key on and closes with a ground signal from a pressure switch on the intake manifold.

I don’t know why that valve would affect shifting.

Why is it getting a ground signal with the engine off? Something might be wrong with the pressure switch.

Are you sure it isn’t the heater valve clicking?

Sixto
98 E320s sedan and wagon
02 C320 wagon