Take a look at the wiring configuration of the light switch.
Light switch outlet combo wiring diagram.
In this diagram the switch built into the combo device is wired to control the gfci outlet itself.
This page contains wiring diagrams for household light switches and includes.
The light on off operation can be controlled through the gfci switch while the ordinary outlet is directly connected to the gfci load terminals.
The neutral is connected to the neutral silver.
Socket outlet wiring diagrams.
Also included are wiring arrangements for multiple light fixtures controlled by one switch two switches on one box and a split receptacle controlled by two.
If you only see one then a switch outlet combo is not compatible with your setup.
Wiring a gfci combo switch outlet with protected light outlet receptacle.
Wiring a light bulb with combo switch and outlet.
If you see two different sets of wires coming into the box then you re good to continue.
The source neutral is connected the line neutral terminal.
The source hot wire is spliced with one of the switch wires and the other switch wire is connected to the hot line terminal on the device.
Fishing in a wire from the receptacle to the light fixture is fairly easy so this is how you would wire the switch receptacle combo device in this situation.
Wiring diagram for a switched gfci combo outlet.
In this simple wiring diagram the combo switch outlet is connected to the 120v ac supply through cb.
A switch loop single pole switches light dimmer and a few choices for wiring a outlet switch combo device.