Jon,
I had new chassis batteries installed by Interstate last month and when I checked them this morning one of the batteries checked in with 7.2 volts and the remaining ones were all at 12.6 to 13.2. I hope a bad battery is all that it is. It appears that Steve and you were correct about a direct 12v connection from one battery to the ECM. I checked the connection for corrosion and there was none. The connection to the ECM was also clean and free of dirt. The 12v direct connection to the ECM was also the battery that showed the low voltage. Interstate's service centers are all closed this weekend but I'll change the battery out early next week and see if that corrects the problem. Thanks again for your help.