2 fuses:
one on back of radio (need radio keys to remove)
other in fuse panel (driver footwell - diagram on inside of panel).
However, suspect fuses are not the issue as they control power supply TO the radio itself. If blown, you wouldn't be able to turn it on. So, we might need some more details...
Do you have rear speakers? If so, are they connected to amp or h/u? If h/u, then likely issue is amp (why you can hear some but not much).
OEM amp or aftermkt?
Let us know more details to help further...
