I just wanted to post, in case this happens to someone, that it is possible to put too much oil in a prius Gen II and cause a red triangle where the car won't shift out of neutral. I know because I did it about a year ago. I was changing the oil on my 06 and lost track of how much I had put in. After the oil change after driving for less than 1 minute I got a red triangle and the car wouldn't shift into drive or reverse, just neutral. I pulled it back to the house with my tractor, and did a little research. A number of people had the issue and were told in message boards that too much oil couldn't be the cause. I decided that it might be. I drained about a quart of oil and it resolved the problem. I think I put one quart too much in the car. So it is possible to create a red triangle and a non-driving Gen II from simply overfilling the oil.
Overfilling by a good amount can cause the oil level in the crankcase to rise up to the spinning crankshaft. The spinning action will foam/froth the oil with air bubbles. Pumping oil full of air bubbles will cause a loss in pressure=red light.
I don't know. It was probably a stupid amount. I was pretty distracted. I'm not saying I'm smart. I'm saying it's possible to be dumb enough to put in enough oil to cause a red triangle. I just put it on here in case someone else has the issue after an oil change. They can save themselves thousands of dollars (potentially) - towed to the dealership, hundreds of dollars for diagnostics, and they pay the gullibility tax of whatever the dealership says they have to replace (the engine?) to cure a simple overfill of oil.