Help needed CEL 1999 E320 P0715 code
 

I need a little help concerning a 1999 E320 with approximately 57k miles. The check engine light is on and the car is in limp home mode. The code was read at AutoZone and he got a P0715 code. I'm not sure if he tested for more. A few questions
a. What does this code in this application represent?
b. Can AutoZone reader be accurate?
c. Would the tranny indicating a malfunction make the CEL illuminate?
Thanks for comments and assistance in this matter.

PO 715" Turbine Speed Sensor Circuit Malfunction "
Most OBD II readers should be able to retrieve that code.
As far as I know, yes a transmission code can trigger limp mode.
Maybe MB DDOC will see your post and provide suggestions. ;)

After doing a search on Turbine Speed Sensor I came accross this thread which is similar

PO715 code

It is from the ML threads.