Since the isn't much easily found info on diagnosing the blinking red light codes on the G&G ETU, I figured I would make a post with my experiences.
So most recently, on a freshly installed ETU which was replacing one burnt in a lipo meltdown, was working fine for me when returned to the owner, but when they plugged everything in to go play, they would plug in w battery, and pull the trigger, and the gun did nothing. The mosfet blinked when the trigger was pulled.
Issue: motor connectors were not securely connected.
Luckily it was a nice easy fix. But other possibilities might include:
-low battery voltage
-sector in wrong position
I am not sure what all other possible reasons it might blink, but as people encounter it, feel free to add to this thread so we can figure things out and have a resource for those looking for answers.