OK, thanks for confirming.
1) Since the garage is a separate building, the National Electrical Code requires that the building have a "means-of-disconnect" to kill power to the garage. Since the circuit terminates directly to the garage receptacle, you have a code violation as there is no "means-of-disconnect". You need a ON/OFF snap switch installed at the garage prior to terminating on any other wall receptacles and/or garage lighting switches.
2) At the garage receptacle, measure the following:
1st turn the breaker to the OFF position and back the garage receptacle out from the wall but do not disconnect any wires. Turn the breaker back to the ON position.
A) Measure from the brass screw (hot) to the silver screw (neutral)....should measure approximately 120 volts.
B) Measure from the brass screw (hot) to ground (green screw).....should measure approximately 120 volts.
C) Measure from the silver screw (neutral) to ground (green screw).......should measure 0 volts or very close to it.
3) If the branch circuit wires are inserted into the receptacle back-stab insert holes, re-wire them to the side terminal screws.
4) Is the house receptacle or the garage receptacle or the circuit breaker
Reply back to me with the 3 voltage measurements.........Thanks.......Kevin!