Product review (5 stars): This Worked for me! - Whirlpool side by side refrigerator.
I had my doubts but this little tool worked for me.  It took me about 4 or 5 syringe refills but it cleared the blockage.  Less than 5 minutes total.  I could hear the solenoid valve working and could have pulled the water line out of the valve but then still would have had to thaw out the freezer door.  Clever idea.