The IC, transmission computer (TCM), engine computer (ECU), and the traction module (ETC), and the Electronic Ignition Switch (EIS) are on the same signaling bus called "CAN bus". If the IC is acting up, it may prevent other modules to talk to each other, therefore, no start. The EIS needs to communicate and handshake with the ECU for a start to happen. I would concentrate on the IC, and find out why it is not lighting up. I asked you to check fuses 4 and 7 and check the voltages on them when the key is in position 2. Have you done it ?