<<Also tried checking the engine flash code according to the DIY procedure and there is not even a single flash. Can this mean a problem with the ECU?
If the LED comes On when you hold the push button and no
codes come back [ no single flash], then the codes have recently been cleared.
If no Led when holding, you prob don't have the key on......
This LED is for emmission codes only.... you need to make the tool and go to other sockets for complete code retieval