Prius loud exhaust on startup

Sounds familiar! I had a similar problem with my old Volvo V70. Different car, I know, but the symptoms you describe – loud exhaust, especially on startup, plus an error code – were almost exactly what I experienced. In my case, it turned out to be a faulty flap actuator in the exhaust system. Does the noise persist or does it disappear after the engine warms up?

Interesting! It does seem to quiet down a bit after the engine warms up, but it's still louder than it used to be. What exactly is a flap actuator, and what does it do? And how much did the repair set you back? Just trying to get a sense of what I might be looking at here.

Okay, if it quiets down a bit when warm, that strengthens my suspicion. The flap actuator basically controls the exhaust flaps, which regulate the exhaust flow. They help with things like emissions and engine efficiency. When they fail, the flaps can get stuck, causing all sorts of noise and potentially affecting performance. I would recommend visiting a local workshop. They should be able to figure it out. I ended up with a pretty hefty bill, around 350€.

Thanks for the info, that's super helpful! Sounds like I should probably get it checked out sooner rather than later. I got it checked at my local workshop and it was indeed the exhaust flap. They quoted me 190€ to get it fixed. Thanks so much!