The most common problem when a APPS sensor is failing is a "Dead Pedal" You'll be driving down the road and hit the go pedal and NOTHING. A real annoying problem. The most common codes are the 0121,0122,222,223 code.
Another issue is a surging or a bucking, this often times will not throw any codes.
The other cause of the "Dead Pedal' is a failing vp-44 injector pump.
Common codes for Injector pump are 0215,0216,1688,1689