I had the same problem and jacked up the left side of the car only, placed jackstands in place. Next, I brushed away all dirt and blew away debris around the solenoid with compressed air. Then, using a 12mm socket with a welded handle similar to a horseshoe, was able to remove solenoid bolts. The solenoid just comes off, as it is a surface mount and doesn't fit down inside the transmission. Using a mirror, I was able to inspect the top surface to make sure it was clean and covered it with a rag while I inspected the solenoid.

Mine was non-functional and digging down through the soft potting compound on top, did not find any bad wires to fix, so the problem was deeper. I needed to go on a long trip, so I had read where you could make a passage between the inner and out o-ring grooves to allow oil flow all the time. This is like having the OD activated (OD light out). I also removed the inner o-ring since I wanted the oil to flow all the time. After reinstalling it, it's working great after 2000 miles. BTW, I used a small, sharp chisel to make a passage between the outer and inner o-ring cavities. Since the solenoid was shot, I had nothing to lose.