trans not shifting properly
 

hi i just got a 2002 deville
the car has 138000 runs great but i have a trany problem.
the car will not shift into 2nd gear the car will shift though all other gears
if i tach car up to 2500 let off gas it will shift into 3rd and then drive fine
i have pulled code p0752 was wondering if i get this part replaced and a trany service if this would correct the problem
really do not want to replace the trans