Rinse your yellow split peas in a colander until they are thoroughly rinsed, and any bad ones have been removed.
Clean and dice your celery. Peel and dice your onion, carrot, garlic and potatoes.
Place the vegetables in the instant pot along with the tinned tomatoes.
Set the instant pot to sauté and cook for 2-3 minutes, adding in your seasonings as you go. You want to get your vegetables loaded in the seasoning.
Add in the yellow split peas, turn off sauté and add in 1600ml of water or vegetable stock and mix well.
Place the lid on the instant pot pressure cooker and select the soup setting and change the time to 20 minutes.
Allow natural pressure release for a further 10 minutes.
When you release pressure there will not be much pressure left to release and give it a quick stir.
Using a hand blender, blend the lumps of potatoes and some of the celery and carrot. Only do this for about 15% of your soup as you want to blend a bit of it to thicken up the soup.
Serve while still warm.