An implantable infusion system comprising:a pump mechanism fluidly coupled to a reservoir to receive fluid contained within the reservoira catheter comprising a delivery lumen fluidly coupled to the pump mechanism, wherein the delivery lumen extends to a delivery region in the cathetera pressure sensor positioned to monitor fluid pressure within the delivery lumen of the catheter and provide a pressure signal representative of the fluid pressure andcontrol electronics connected to receive the pressure signal from the pressure sensor, wherein the control electronics further:measures decay time in the fluid pressure after a selected pulse based on the pressure signal, wherein the decay time is the time required for fluid pressure within the delivery lumen to fall below a selected threshold pressure value after a selected event corresponding to the selected pulsecompares the decay time to a selected decay time anddetermines the existence of a catheter malfunction in the form of a leak in the catheter if the decay time is below the selected decay time.
