I'm glad you got it working! You might want to reinstate the code you commented out, modified so that it is still sensitive to the open-circuit bit, because thermocouples do sometimes go open-circuit - although it's usually the EGT ones rather than the CHT ones in my experience (of a PA28R with a turbocharged Continental engine). That's on the assumption that the fault detection can still detect an open circuit thermocouple when the T- pin is grounded - but you can easily test that.