It's the one thing that strikes fear into almost everybody's heart: Your car is messed up, you don't know what's wrong and if you take it to the mechanic, you’re probably going to get taken for a ride.
So what if there was a phone app that could diagnose your car for free, tell you what is wrong and what to do to fix it? That's what Car App promises.
But does it actually work? Our tech reporter Rich DeMuro put it through the paces.
Watch the test in the video above.