Before you box your PS3 back up to send to Sony, try these three easy PS3 repairs first:
1. Restart your PS3 and wait about 30 minutes. Then, fire it back up and see if this helps. There have been a couple of times that I've had this happen and had to turn it off for about 2 hours, and then everything was hunky dory again. Sometimes, just like a computer, it just needs a break.
2. Check all of your cables to make sure that none are loose. Any cable that plugs into your PS3 can easily work it's way loose, especially if you have the controller cords are stretched.
3. Gently take out your hard drive then replace it, as sometimes this can reset everything back to the original settings. (There is more about replacing your PS3 hard drive here on Bright Hub.)
Normally, if your PS3 has just gotten overheated, one of these simple fixes will clear up your blinking yellow lights. If not, then the problem might be more serious.