Can you help me with a P0017 code

I recently changed the thermostat and temp sensor to clear codes and remove the check engine light. After putting everything back together, thr next day the car started running very rough and stalling, I check the codes and got P0017. The check engine light has not come back on. I removed the code and it ran good, but now the code is back. still no check engine light. could this just be the computer or do I need to start replacing solenoids and sensors,


Gerry