Error PO725 2008 Sentra
 

Can anyone tell me what this code means and where is the part located in order to replace it?
The car will stall out now and then when I come to a stop and has been rough when starting it up.
It also had a few other codes but some may be older codes that have been fixed.
The po725 said Trans Engine speed sensor
Also had a po171 System to lean, P3631 and a P0011 Intake cam over advanced.

Thanks