Here is the thing:
When you get the Quad driver code in addition to other codes, you are supposed to fix the other code problem first, and then check to see if the quad driver problem goes away.
I would have started by replacing the throttle position sensor first. Interesting how replacing the charcoal cansister valve fixed that.
Anyway, you need a good diagnostic to isolate the cause of the quad driver fault. Do you have a service manual? It'* very possible it is the TCC solenoid, but you can't say for sure.
One place you can start is by checking the wiring to the transmission. See if it is burned or chewed by mice or something like that.
1999 540iA Sport
Former 93 SSEi Owner
Former 89 SE Owner