When operating with a stock battery, there is a sensor (variable resistor) which feeds back info on battery temp to the control board-- at a certain threshold, it tells the control board to close the relay for heating element power thereby heating the battery pack. The control board looks at the relationship between the incoming resistance value and the heating element relay status-- if it sees a mismatch (i.e. resistance value indicated no heating needed yet heating relay is closed) you will get an error code. The relays in the shc control boards are notorious for sticking-- I think what is happening here is the heating element relay is cycling and remaining on. After a while, the ecu sees the mismatch and triggers the code.
Using a fixed value resistor, in this case providing a feedback value for "no heat required", will have no effect on operation other than to tell the ecu that the battery heating element is not needed. It has no other correlation with any temperature sensing. In other words, the heater has no way to compare the temperature read by the sensor on the control head with the battery temp sensor, or the overtemp sensor on the body of the TEG.
I am willing to bet that if you check your heating element relay, you will find that the relay remains in the closed position after startup. In short, your ecu is being told that the heating element is not needed, yet it is seeing the relay status as "on", and essentially saying "what the he** is going on.
I should also add that the ecu cannot tell if the heating element is attached or not-- it can only see that the relay itself is closed and sending power down the line towards it.
