I've been checking on this thread just to see if you ever came to a solution. My prelude had the same thing happen with 2 ECUs and I never figured it out either. I remember replacing the main relay lessened the problem, but it never was 100%.
That being said, your situation sounds a bit different. If it's only on hot/warm start, it would lead me to believe it's almost certainly something electrical and in the engine bay. Like maybe something is expanding from the heat of the engine (which is no longer being dissipated by you driving and moving cooler air over components) causing a connection not to be correctly made any more after it sits and bakes for a bit.
Checking grounds is the first thing that comes to mind in this situation, and they're also relatively cheap to replace....sadly all I have is that as a jumping off point. Nothing else is really coming to mind.
That being said, your situation sounds a bit different. If it's only on hot/warm start, it would lead me to believe it's almost certainly something electrical and in the engine bay. Like maybe something is expanding from the heat of the engine (which is no longer being dissipated by you driving and moving cooler air over components) causing a connection not to be correctly made any more after it sits and bakes for a bit.
Checking grounds is the first thing that comes to mind in this situation, and they're also relatively cheap to replace....sadly all I have is that as a jumping off point. Nothing else is really coming to mind.