I hear the pump is quite difficult to replace - its located deep down. And the cause of failure is usually a faulty check valve. The valve can get sooty and cause water to leak into the pump knackering it. I could suggest testing the check valve for soot by unfastening its hose and probing with your pinky (this is easy). If there is no error code, and there is soot, clean the check valve and replace if need be. Its (apparently) an easy fix.