2002 Citroen C5 1. automatic gear fault 2.6800 code fault

2002 Citroen C5 V12

helllo
i have 2 problems
first problem is : after few km i have the message - automtic gear faullt and the servicr lighting, somtimes the car make a real noise from the gear.like a shoke
the second problem is - 6800 code
please tell me what is this

thank you
Jacob
Israel