master control warning triangle flashing on and off

So driving down to Southern pines yesterday with the plastic trailer empty to pick up a Whirlpool duet washing machine all the way down empty from the house to Southern pines no issues car drove like a dream like it always does We don't expect anything else from this car. Drop the washing machine on the trailer put up the tailgate heading back to where we just came from this is an hour and 21 minute drive on the way back the master control warning triangle kept coming on which put on the problem word across the top of the MFD then the master control light would go off the MFD car would turn green so on and so forth all the way back home when the master control warning light was on the car wouldn't necessarily skip or miss but it wasn't running as smooth as it was just a second ago when the light wasn't on and it seemed to happen when we were going down the road at a good clip 60 mph let's say. At one point I pulled over didn't turn the car off but engine was not running car was on I checked the oil I checked the temperature of the hoses top and bottom etc everything felt perfectly normal no smells under the hood nothing soon as I get back in the car and get up to speed the lights turning on and off again No worries oil is full seems to be pumping getting close to time to change yes and the coolant is full and the hoses feel very normal not even close to being near and overheat condition so I press on it speed get home uneventfully still the same thing and no codes other than my standard PO420 that has been in this vehicle for 5 years now and the TPMS sensors all four of them very strange.

 

The only thing the Toyota software found that the autel AP200 did not see was the CM monitor stopped code I think it's 1271. But I'm not sure I'd have to open up the laptop to look again but I was shocked to see that code the CM monitor hasn't stopped and God half a year now and this car has never had that code even though I've been through three different CM monitor boards the one that's currently in has been in now close to 2 years every few months I'll get in the car push the start button don't see the zero on the speedometer immediately turn everything off reapply the brake hit the button and everything lights up but I wouldn't think this would make my master control warning triangle flash on and off.? Then the other thing I did was undid the radiator cap and slowly kept pouring coolant in for what seemed like 30 minutes and maybe a third of a gallon jug which is interesting because there's no leaks and it's been full for the last 3 years.

 

Gosh I hope not we've been using this 300 lb empty plastic f l o e trailer for about 5 or 6 years now behind a generation 3 first and my sienna van and then behind the '09 generation 2 and have never had a code or a flash or anything and we've moved some quite heavy things even up in the mountains We didn't push it and do foolish things but we have moved some pretty heavy stuff 2000 lb on the trailer pretty much flat land but never had a code or anything and we don't have a lot of pushing and pulling going on with the trailer we're careful and we match speed We do what we're supposed to be doing generally the lightweight trailer and what's on it generally is only about 200 lb so we're talking about a trailer and item weighing in it 750 lb total generally usually a lot less than that and then if it's any heavier than that it's only going a block or two in the neighborhood or something.