Probably a clog in the EGR
did you recently pull the horn fuse? That's what happened when i did
It means that your PCM has detected somethign wrong with your egr system. I have never done this to a toyota, and don't even know which parts it has and doesn't have. follow along and check what...
If it starts but doesn't stay running after you release the key from the start position, it means your ignition switch is bad. Not a huge expense.
It holds about 20 gallons of gas
Possibly the "Related Questions" below will be a starting point to dealing with this EGR problem...