Originally Posted by Eddiec1564

The ECU does a electrical check of its system just before you start the engine. Sounds like you have a shorted wire somewhere. Or possible a bad ECU(shorted driver for that circuit)

You said you have continuity from the ECU pin 53 to the transmission connector pin 4. But did you check for continuity with other pins of the ECU to that pin 53? There should be no other continuity with any other pin with ECU and transmission harness disconnected. If that is good. Then replug the ECU back in(hope you had the battery disconnected during these testes). Remeasure continuity again from the ECU pin 53 to other pins. It will be hard to back probe the ECU harness in place, but I use a straight pin to poke into the wire. There should be no continuity, if so, then the ECU is bad.