I just got a local FD owner that believes he shorted out his water thermo sensor. He was driving along and heard what he described as an electrical short. He opened the hood and could smell something burning. His ECU posted check engine code #9.

QUESTIONS:
(1) What is check engine code 9?-He believes it's related to the water thermo sensor.
(2) Are the water thermo sensor and water thermo switch interchangable? -He ordered the water thermo sensor from mazda and surprise surprise they sent him the wrong part. He said they look the same and wants to know if he can use the thermo switch in place of the sensor.

I have no experience with this problem so for his sake I am seeking advice.