Right, so you need to disconnect the battery, and unplug the ECU and the plug on the coil, and do a simple continuity test on the LT wires.

Indeed the crank sensor merely tells the ECU when the engine is at 90 degrees BTDC, so theres either a wire gone open circuit or the ECU has an internal fault.

If the LT wires are all ok try another ECU, should be a simple fault to fix