It could be the wiring harness as others have said, it could also be the EH portion of the steering valve, another possibility that we have seen is that the steering angle sensor will not mount properly because the shaft that it sits over is slightly too long and causes binding of the sensor which throws it out of spec at times, loosen the mounting screws and watch closely to see if the sensor lifts and won't sit all the way down on the casting without tightening the screws. If you find this being the case simply file the shaft off until the binding is gone, doesn't take much.