To start off, I have been dealing with this issue for weeks to no avail on my wife's 2001 Civic EX with an Auto trans. The issue manifested as a complete loss of all gears once the car is driven for about 20-30 minutes. The transmission shifts and drives just fine up to this point. Every single person I mentioned this to kept saying replace the trans. So I did and guess what? It changed absolutely nothing. I pulled and swapped in a trans from a 2003 EX with 128k miles, trans shifts smooth as butter and the car even gained acceleration power. Unfortunately, the same thing happened, after driving for about 20 minutes with no signs of failure, no codes, and fluid that is bright pink because I just changed it, the car just loses all gears. For whatever reason, I am able to cycle the key and drive it again seemingly with no issues. I feel like I'm at a loss battling a war I can't even win. My thoughts are that if something was a hard fault, it would set a code. Does this sound like intermittent TCM or ECM loss? Has anyone ever dealt with this before? I'm not down on much money because of this car, but I just spend the entire week sourcing and replacing the transmission that didnt even fix the issue in the end. Any help would be greatly appreciated because I feel like I'm just out of the loop with Honda's with an auto trans. I have owned several Honda's auto & manual and have never come across this.