I have a MT 250 running the heat on the hot tub in the gym I work for and I keep getting a random E01 code and the heater shuts down. I have been able to determine that E01 is referring to a temp sensor error, but can not find any information on how to actually diagnose the problem. The heater will reset and work fine for random periods of time but will eventually set the E01 code and shut down. I don't want to throw parts at it without determining the actual issue first. Is there any info on how to test the sensor and/or a diagnostic chart to follow in order to test the circuit? I have the owners manual and it doesn't have anything in it about the code. Thanks in advance for the help and thanks to everyone in here that has posted in the past. I have been able to diagnose all the other problems and answer any questions I've had to this point just by searching.