I have problem with Navien NCB-190/060H Error Code E031-00

[Rockyyang]

Update
Today i try to unstand the error code from what Sensors.I knew the Heater Shoutdown abnormal and gave Error code should control by one or more sensor.I test sensor which related. one by one disconnect and Connect it.I Found out the Error Code is from Thermal Fuse when i disconnet it will Error 031-00.Something wrong with it cost this problem i thinks it not melted totally。
The Thermal Fuse it is prevent Your Heater overheat when the Temperature up to 120° 248F It will Locked down the Heater. I had doubts thermal fuse before but i don't test serious. I thiks it has problem should melted.
I hope my idea is right ！

 

[Fitter30]

Check the air filter incoming air top left just inside cabinet. Fault E30 230° for 10 minutes trips. Have you done the yearly flushing service with pump and vinegar? Pull that thermal fuse check for soot.

 

[Sponsor]

 

[Rockyyang]

Check the air filter incoming air top left just inside cabinet. Fault E30 230° for 10 minutes trips. Have you done the yearly flushing service with pump and vinegar? Pull that thermal fuse check for soot.

The problem is solved after change a Thermal Fuse.
Thank you so much for your help.