Circuit Breaker Tripped

• One possible cause of a garage full of nonfunctioning outlets is a circuit breaker having been tripped. Circuit breakers have taken the place of fuse boxes in newer homes. A circuit breaker will break the circuit of any electrical zone that has a malfunction, such as a short circuit or a voltage overload. Examine your circuit box to see if one switch is thrown, facing the opposite direction from all of the other switches. Flip the circuit back, and test your outlets.
  
  

Blown Fuse

• In older homes, there may still be a fuse box in use. Fuses work to cut power to portions of the house when a certain voltage is exceeded. Check the fuse for your garage, and ensure it has not been blown. If it is blown, replace the fuse and test the outlets. Once confirming a blown fuse was the issue, ascertain what caused you to exceed voltage to your garage, which can be caused by running too many power tools or devices simultaneously or an improperly wired fixture.
  
  

Issue at the Junction Box

• Another potential issue that can cause all of the outlets in a garage to be nonfunctional is a problem at the junction box, which is the electrical box, likely in your attic, from which all of the outlets in your garage receive power. Flip the circuit for your garage off, and examine the box for signs of damage or broken wires. Once you have verified that the box is wired properly, turn the power back on and retest your outlets.
  
  

GFCI Outlets

• Some garages will have what are known as Ground Fault Circuit Interrupter (GFCI) outlets. These outlets are common in kitchens and bathrooms as they are designed to have a built-in circuit that prevents electrocution by cutting power when a voltage is exceeded. With some newer outlets, one outlet having its GFCI tripped will cause all other outlets in the room to be shut off as well. Examine each GFCI outlet in your garage, and depress the reset button on each. Retest your outlets once you have verified that all of the GFCI outlets are reset.