Check Engine "Injector failure Code"

[YarisPR]

Hey

On friday morning I started the car and suddenly the "Check Engine" light was on. I drove the car all day until noon when I disconected the battery and the "check engine" light turned off. But satuday night it was back on. So I call a friend and we scan the car and the code shown was; the problem was in the Injector of the forth Cylinder. Weird thing is the car works just fine and all the other things were normal except that code. We clear the code with the scanner but I'am still worried.

Have u guys seem something like this? What can it be?