Add the corned beef to the Instant Pot.
Add the quartered onion, crushed garlic, pickling spices, and the liquid. The liquid should cover the brisket. If needed add another cup of liquid. Make sure you do not go over the MAX fill line.
Put the lid on your Instant Pot and set the valve to close. Cook on High Pressure for: - 75 minutes for a 2lb brisket - 80 minutes for a 3lb brisket - 85 minutes for a 4lb brisket *If the brisket is thicker than 1.5 inches, add 5-6 minutes for every .5 inch
When finished, let it have a NPR of 15-20 minutes before you vent it and release pressure.
Set the cooked brisket in a deep dish or container. Transfer 1 to 1.5 cups of the liquid with it.
Add your steamer basket into your Instant Pot to make it easier to the veggies.
Add the potatoes and carrots. Add the cabbage wedges on top of them
Put the lid on your Instant Pot and set the valve to close.
Cook on High Pressure for 3 minutes followed by a quick release.
Open the top and remove your veggies by carefully pulling out the steamer basket
Cut the brisket across it's grain into slices and serve with the vegetables.
Strain the liquid and pour some over the brisket before serving. Store remaining brisket in the liquid in an airtight container.