Rear Brake issue - 0ne light on dash present (!) relating to Brakes

I have never seen this issue before. '05 with 185,000 miles and NO ISSUES. I removed the SKS fob about 20' away from car, I DID NOT D/C the 12 V battery, and then jacked up rear to check brakes. Drum was a little bit rusted so I hit it with penetrating lubricant and hit the brake drum a couple of times before it came free. I checked the brakes and replaced the drum and wheel, and took car for a test drive. Immediately as light came on the dash: the one with a ! inside the circle with ( ) around the circle. So a brake issue. I used TS to check for codes. I tried to check the ECU for the ABS system BUT there was an asterisk: * which meant that that ECU could not be checked for operation. Maybe a fuse blew? So I then checked ALL the fuses and found all GOOD. I did not check any relays. What's next? Possible skid control ECU? I am having a hard time understanding WHAT happened to cause this and now what the repair is... Did hitting the drum cause an issue with an ECU? You professional advice is welcome! Thanks in advance.

 

Thank YOU Chappy. I have not used blink codes in a long while... I will give this a try! So that particular light on the dash will blink the code(s) that are present with that light and I just need to count the blinks to get the info code and look it up, yes? And maybe I can erase codes the same way... meaning use the jumper wire.