GMC Sierra Denali 1500 2023 Owner's Manual page 219

218 Driving and Operating
cord may exist, which will prevent engine
heater operation at temperatures above
18 °C (0 °F).
Warning
Do not plug in the engine block heater
while the vehicle is parked in a garage or
under a carport. Property damage or
personal injury may result. Always park
the vehicle in a clear open area away
from buildings or structures.
To Use the Engine Heater
1. Turn off the engine.
2. Check the heater cord for damage. If it is
damaged, do not use it. See your dealer
for a replacement. Inspect the cord for
damage yearly.
3. Plug the heater cord into the connector
on the vehicle.
4. Plug the cord into a grounded 110-volt
AC outlet that is protected by a ground
fault detection function.
Warning
Improper use of the heater cord or an
extension cord can damage the cord and
may result in overheating and fire.
Plug the cord into a three-prong
electrical utility receptacle that is
protected by a ground fault detection
function. An ungrounded outlet could
cause an electric shock.
Use a weatherproof, heavy-duty,
15 amp-rated extension cord if needed.
Failure to use the recommended
extension cord in good operating
condition, or using a damaged heater
Warning (Continued)
or extension cord, could make it
overheat and cause a fire, property
damage, electric shock, and injury.
Do not operate the vehicle with the
heater cord permanently attached to
the vehicle. Possible heater cord and
thermostat damage could occur.
While in use, do not let the heater
cord touch vehicle parts or sharp
edges. Never close the hood on the
heater cord.
Before starting the vehicle, unplug the
cord, reattach the cover to the plug,
and securely fasten the cord. Keep the
cord away from any moving parts.
5. Before starting the engine, be sure to
unplug and store the cord.
The length of time the heater should remain
plugged in depends on several factors. Ask a
dealer in the area where you will be parking
the vehicle for the best advice on this.
(Continued)