The problem is with a linear positioning system. The card is 1756-HYD02 2 Axis Hydraulic Servo. The error given in controller properties is a loss of encoder fault. The temposonic in the cylinders have been changed and the wiring all checked. It is happening on more than one machine that have dedicated processors but use the same type card. I have the option not checked in the cards properties to give me a major fault and can find nothing in controller properties that will cause this fault to occur. When trending the feed back of the axis on both machines it is on target always.