Hi Jeff,
if you use yor CAN card and the ECU as receiver only, there is no way to avoid the Error, when your ECU is turned off.
You need at least one lisener to acknowledge the sent message.
You can short the Port 1 with Port 2 if you have a two Port CAN Card available to use the second port as "Spare"Receiver, when the ECU is turned off.
I dont see a way to avoid the Error Message if the Error did occur without changing the Driver.
Hope this Informations can help,
Stefan Henke
NIG