Rechecked all the ground wires and cords to make sure all appropriate wires were included when hooking up new batteries. Nothing looks missing. In fact, didn't even take bolts off at terminals, just loosened and slid off so as not to lose any connecting wires. I did get the correct batteries, 65S.
Tried to do the on-off-on-off-on thing quickly but got no codes. The check engine light just blinks rapidly and I hear a loud clinking sound, not like you get with a dead battery. This clicking is happening when I turn the key in the on position b4 I get to the cranking position.
Also, not sure what you all are calling the ECM. I don't know exactly what that stands for. I'm not worth much under the hood. Thanks for all of the help so far.