We too have a 2002 Prius and have smelled a burning smell on two occasions. We have not figured out what it is or where it came from. I took it to the dealer and they could not smell it. They suggested it might be from the hybrid batteries but the smell seems to be in the passenger compartment only; not in the engine or the trunk.

The first time it happened was a couple of weeks ago and then it went away. I thought that it smelled like coolant hitting a very hot surface. The second time it happened (yesterday) my wife thought it smelled like pot. That is very different from the smell the first time so it is remotely possible they are not related.

That's all I know right now.

 

Found out more information

Okay so we dropped the car off at the dealership (first of all why can't a person drop something off and then actually be able to hear a good phone call from the dealership), they told us first off that the crankshaft battery is bad and before they can do a diagnostic check ($49.95) the battery had to be replaced ($206 with labor). Then they just called me and said that the left front bulb area melted along with the wires nearby and that's why the fuse kept blowing in the tail light area along with why we smelled the burning as well coming from the engine area under the hood. $121 to replace that, so far including getting an oil change it is going to run me just over $420 to get it fixed. At least the rental is free! I will keep everyone posted on any more updates.