GMC Hybrid 2007 Owner's Manual page 12

Some electrical devices, such as motor-driven
appliances and tools, have high start-up currents.
During this start-up period, the 120-volt AC
supply will attempt to start the electrical device for
up to five seconds. If the current does not fall
below the maximum 20 amp rating of the
APO within this five-second timeframe, the system
will shut down the outlets and the light next to
the APO button will flash, while at the same time a
120V OVERLOAD message in the DIC will
appear. This type of situation is unlikely, but if it
does happen, press the APO button and try to start
the electrical device again. If the electrical
device fails to start a second time, it is probably
because the device needs more start-up power
than is available.
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The Ground Fault Detection (GFD) system checks
for leakage current to ground, or the truck
frame, that could potentially be a shock hazard, in
much the same way as the Ground Fault Circuit
Interrupt (GFCI) outlets protect you in your home.
The GFD self-test is automatically performed
during the activation of the APO system.
Thereafter, if the GFD system detects a significant
leakage current, it will immediately shut down
the outlets and the light next to the APO button will
flash, while at the same time a 120V GROUND
FAULT message will appear in the DIC. If this
happens, unplug all electrical devices and reset
the system by pressing the APO button. Then plug
in each electrical device individually until the
malfunctioning extension cord or electrical device
is identified.
If, after unplugging all electrical devices and
cords and resetting the system, either the
120V OVERLOAD message or the 120V GROUND
FAULT message continues to be displayed,
have the vehicle serviced.