Cut the racks of ribs in to sections that will fit in the pressure cooker and rub with salt and pepper.
Place onion, celery, carrot and beer in the pressure cooking pot. If you’re going to make sauce from the juices in the pressure cooker you can place the ribs directly in the liquid or put the ribs on the rack if you’re going to finish the ribs on the grill or under the broiler with another sauce.
Close and lock the lid of the pressure cooker. Select High Pressure and set the timer for 12 minutes. Press start.
When beep sounds, turn off pressure cooker and use a natural pressure release for 10 minutes and then do a quick pressure release to release any remaining pressure. When valve drops carefully remove lid.
Remove the ribs and cool to room temperature. Once cool, refrigerate until ready to serve.
To finish the ribs:
Preheat the BBQ grill to a medium high heat. Coat one side of the ribs with BBQ sauce and grill 3 minutes. Coat the other side with BBQ sauce flip and grill an additional 3 minutes. Slather on additional BBQ sauce and grill each side for an additional 3 minutes.
You could do the same as above by broiling them until just how you like them.