Transmission shifter solenoid circuit malfunction?
 

My 2004 986 is showing the "Check Engine Light" and a rocking, rotating display light on the dash runs back and forth between high and low gears. This is an automatic transmission. An engine sensor read out says "Transmission shifter solenoid circuit malfunction". I cannot find anything on line about repairing this. Does anyone have a clue please?

Water pump went out and we replaced it and the thermostat. We are thinking possibly the water pump blew coolant into the shifting mechanism causing the solenoid issue. Please let us know if you know the direction to go with this.