Dishwasher isn't cleaning dishes, cycles through steps quickly. When checking found that the wash pump is turning, water starts coming through the spray arm but at very low pressure. Impeller is connected to motor shaft. Don't know why pump isn't building enough pressure to push out spray arms. Arm is not plugged and pump cavity is clean. Tested this without filters in bottom of dishwasher. Appears there are two pumps in this unit, one for draining and this one for washing. Any ideas what may be wrong??

I transposed the b and d on the model number. Don't have it with me, believe it should be GPDB998JC0. What I found last night is that the impeller and "blade" are mounted in a plastic sleeve which is connected to the motor shaft, the drive mechanism is a spline on the motor shaft. The spline was stripped out on the plastic sleeve so the impeller would turn initially, saw a little water come out of the spary arm, but would then drop off to nothing. Used epoxy to fasten plastic sleeve to motor shaft and will order a new assembly next time there's a problem. Cannot order just the needed parts, must order the entire pump/motor and pump basin for $137+. Thanks for the response.

I have the same problem with a Kenmore Ultra.
I have removed the Arm, Inlet base, and was down to removing the Impeller.

The Impeller is held in by a screw which no matter what I do will not come out. Not stuck, just rotates and nothing happens.. no matter what I do to it or the impeller. Is the only way to get at it to remove the motor from the botom?

The impeller spins and water pumps out, but not enought to turn the lower arm. When in operation I open the door the water pressure goes up and then dies.

I would be greatful for any help!
Thanks,
Doug