PATS showing DTC 16

Engine cranks but will not start. The theft light continuously blinks fast and after sometime it stops and gives out the 1-6 blink code. I tried hooking up an obd2 tool, but it gives an error which means I can not communicate with the car, not only the pcm or any particular module but all. I had the fuses and relays checked particularly the pcm relay, pcm diode and fuel pump relay and all are working fine. I had the fuse box on the engine bay removed to check the underside and all wiring connections seem to be okay. I had the pats key cylinder transceiver ring removed and it seem perfectly normal. By the way, the fuel pump motor and strainer inside tank is new and so is the idle air control valve. I had the inertia cut-off checked also and it is down, meaning it's active. Is there something I might have overlooked?