Keith, I understand you have changed the TSP sensors , have you checked the supply voltage from the vsm to the sensors you can do this by back probing the connectors your looking for 5 v or there abouts. Reconnect the connectors to the sensors and back probe the sensor connector again measure the voltage across the sensor wire to the negative, if it's greater than 0.5v is yes then the sensor is faulty. If the answer is no then cause could be mechanical.