Where is the location of code P0715 for input turbine speed sensor A circuit at ?Thanks.

Notice that the code indicates the circuit needs troubleshooting, not that the part needs replaced. This forum, as well as any other forum cannot answer such specific diagnostic questions; location of the code? You mean the sensor? It is located on the valve body inside the transmission. This kind of concern really requires the knowledge and skill of a real technician to troubleshoot. Here are some shops near you: https://repairpal.com/repair-shops/mercedes-benz-repair-and-service-in-baltimore-maryland