KitchenAid Dishwasher (model KUDS01IJBL) has black gunk inside

That black gunk is caused by soap deposits and food particles that do not get washed down the drain. This all collects in the area around the door gasket and front of the wash tub and forms a sticky black sludge. You need to periodically clean the interior of the dishwasher out with a non-abrasive cleaner with some bleach in it to kill bacteria. You should also check the wash pump sump (located under the lower spray arm) to make sure it is not being clogged with food and debris. In order to access the pump sump, you will need to perform the following:

1. Remove the lower wash rack and lower spray arm.

2. Remove the upper wash rack and spray arm.

3. Locate the screws holding in the upper spray feed tube. Remove the screws to the feed tube and turn the whole assembly 1/4 turn to the right (CW direction). The entire assembly will unlock from the wash pump assembly and lift out.

4. Remove the strainer assembly (known as an accumulator) that covers the pump sump area.

Inspect the sump area for food particles and debris that may be contributing to the mess inside the wash tub. If you need some guidance, pcappliancerepair.com has some very helpful exploded view diagrams to assist you.

If you have any questions, or require further assistance, please let me know. I hope this is helpful to you.