So one more thought here - there's either an issue with the module, or, if one of the wires in the harness was either broken, or if the pin wasn't seated in the connector, you can get the same response. So the last thing to do here is to confirm that both amps shunt wires have full continuity from connector pin to the end of the wire. Also make sure that the connector pin is fully seated in the connector (if it's retracted in the connector, it might not be making contact with the module side of things.