Soap Dispenser Does Not Open During Wash Cycle
Here are your parts
Replacement parts for WHIRLPOOL GU1200XTLT3 UNDERCOUNTER DISHWASHER | AppliancePartsPros.com
See the attachment for the tech sheet
This should also help with your repair.
Whirlpool KD-12 Point Voyager Dishwasher Service Manual - ApplianceDigest.com
You may have to join the site to download the manual but it is free and this is a very good site for manuals.
Could be a mechanical or electrical (solenoid burned out) with the dispenser.
May also be a problem with the control board.
16499300.pdf (1.0 MB)