The US Consumer Product Safety Commission states that if ground fault circuit interrupters (GFCIs) were installed in residential circuits, they could prevent over two-thirds of the electrocutions that happen each year. It's a good idea to occasionally troubleshoot your GFCI outlet, as a mis-wired GFCI cannot protect you from electric shock, and if the wrong wires are connected to the wrong terminal screws, they cannot provide power to the GFCI or any other outlet on the circuit.
Plug a lamp into the ground fault circuit interrupter (GFCI) outlet and turn it on.
Press the test button on the face of the GFCI outlet. The reset button pops out and the lamp should turn off. If the lamp fails to turn off, skip to Step 4.
Leave the lamp plugged into the GFCI outlet. Push in the reset button on the face of the outlet. If the reset button fails to stay pushed into the outlet, check the outlet wiring.
Turn off the circuit breaker in the main electrical panel box to disconnect electricity to the outlet. Remove the outlet cover from the GFCI outlet.
Remove the two screws holding the GFCI outlet in the electrical box. Carefully pull the outlet from the box.
Turn the GFCI outlet over and verify the white wire from your power line connects to the silver terminal screw labeled "Line." The power lines connect directly back to the main electrical panel box. Confirm the black power line connects to the brass terminal screw labeled "Line" on the back of the outlet.
Check that the green ground wire connects to the green ground screw on the GFCI outlet. A twist-on wire connector must connect the green wire to the bare copper ground power line wire. Both the bare and green ground wires should connect to a grounding terminal in the electrical box, if the box is equipped with one.
Check the load lines on the GFCI outlet. If the GFCI outlet is located in the middle of a circuit, the load lines connect to an additional outlet on the circuit. The white load wire connects to the silver screw labeled "Load" on the back of the outlet, the black load wire connects to the brass screw labeled "Load" and the bare copper ground load wire connects to the green ground wire from the ground screw through the wire connector.
Tighten any loose screws on the outlet. Reinstall the outlet into the electrical box and replace the GFCI outlet cover. Turn on the circuit breaker in the main electrical panel box to reconnect the electricity to the outlet.
Plug the lamp into the GFCI outlet. Press the reset button once again. If the GFCI resets, the outlet is good. If the outlet fails to reset, the GFCI outlet has failed and must be replaced.