I cannot find the document I need, but I think it is a communication fault.
The TEM, like many controllers can either run the genset itself, at a fixed power level, or take power commands from a higher-level controller via a Modbus link. If there is an error in the data exchange, then I think this is the fault.
There should be a number code for each fault, there will be a table of codes in the manual, which should help you track it down.