Brake lights

I believe the G2 has LED brake lights and regular tail lights (running light). This is probably the light that is out. It's a regular 168 bulb, and you can usually get a pair for around $5 at pepboys (maybe less at Walmart). As with any bulbs, I always recommend replacing both at the same time. It always seems that the other one fails relatively soon afterward if you don't.

 

If in fact the "brake" LEDs are out (these are the six LEDs on top of the rear light housing) then you will have to replace the entire light housing.

Before doing that you might want to ensure that the wiring harness connections are secure.

 

If all the left LEDs are out, suspect a blown fuse or broken wire, before you spend $$ to replace the module.

 

My right brake light (called "Stop Light" in Prius wiring diagram) went out. Turned out to be a tiny amount of corrosion in the wiring harness attached to the body (not the harness that is at the lighting assembly). I scraped it with a tiny screwdriver, applied some Super Lube, which claims to have anti-corrosive properties, and it now works perfectly. Whew!

 

I did have one brake light go out several years ago, and it wasn't the connector, it was a failure of the LEDs. One, and then two, and finally all of them. The consensus at the time was that the way the LEDs are wired, if one goes out, the voltage (or current, I don't remember which) goes up and causes a more rapid failure of one of the another ones. This cascade of LED failures accelerates until all of them are burned out. I did replace that one brake light assembly and haven't had a problem since.

A couple of years ago someone told me that my brake light was out, and sure enough the other one was completely dark. Seemed strange since the first one went out one LED at a time. Before ordering a new assembly I unplugged and replugged the connector a few times. The brake light has been working ever since. Definitely check the connector first, that might be all it takes.