Red triangle and CEL, car will start but switches off of ready mode

I was driving my 2007 Prius today and the red triangle came on and it lost acceleration. I coasted to a side street. If I turn the car on it will make it to ready mode and the red triangle as well as the CEL will come on. However, this will only last about 10 seconds, and then it will exit ready mode and the red triangle light, (!), VSC and CEL (the latter 3 all yellow) will subsequently come on (the tire pressure gauges have always been broken so that warning light is always on...).

Since the it won't stay in ready mode, I can't drive and I can't make it to an auto parts store to get the error codes. After browsing Prius Chat, I didn't see any posts that match the symptoms. Does anybody have any suggestions? Mainly, does anybody have suggestions for very simple stuff to initially check? I just want to make sure it is not some strange simple problem before trying to use my AAA to get it towed to the dealer, which is in a town 60 miles away. Thanks!

 

An update. I realized there was a NAPA store just a few blocks away and they were willing to come read the error codes. It is throwing a P3190. After reading about it, it sounded like the simplest thing was to try checking the MAF sensor. I got it out and found a cottonwood fluff over one of the sensors. I removed it and sprayed it down.

Now when I try to turn it on, there is no longer the red triangle. However, it will not go to ready mode and all the other lights are on. I assume I wore down the battery. I'm going to borrow a friends car and try jumping it after I do a little Googling now. Does that sound reasonable?

 

To be clear, it now goes to IG-ON setting with no red triangle, but all other warning lights are on. But my memory is that it was it is suppose to do. I just realized that maybe I had it in neutral, I will go back to where it is and double check that.

 

Turns out disconnecting and reconnecting the 12V battery made it so it would enter ready mode. So it seems like it was indeed the cottonwood fluff in the MAF sensor that caused the issue. I'm not sure why the 12V battery disconnect/reconnected was needed subsequently to get it to start.