How do I clean moldy dishwasher racks?

Yes, if your dishwasher isn't stainless steel. Stainless steel doesn't like bleach at all, so if you have one like that, clean everything thoroughly by hand the run a cycle with 1 cup of vinegar through it. Use the highest heat setting possible too

Before you start, read this:

https://www.servicemaster-restoration-cleaning.com/2017/03/mold-myths/

I had an issue with one that had been sitting closed for awhile. I put vinegar in a spray bottle and sprayed everything. Then I ran it empty with my hottest water setting and dishwasher detergent. Then, while still wet, after the cycle, I took the racks out, scrubbed them again, rinsed them and dried them on my porch in full sun. I thought running the machine was important in case there was any I couldn't see. A soft brush helps with nooks and crannies. The best small brush I have found for this type of cleaning is a denture brush from the dollar store.

If the racks are plastic coated, you can take them outside and bleach them, but rinse immediately. Bleach is very corrosive.

I would try other methods first.

When you get the mold out, open your dishwasher as soon as the dry cycle ends and let it air dry inside.

I run vinegar through the dishwasher once a month as well as my coffee maker, but I allow both to air dry during the day.