I bought a used 2015 GMC Sierra 4×4 with about 130,000 miles on it, and I’m still finding things the truck has that I didn’t expect.
There’s a USB port tucked inside the glove box. There’s also an outlet that looks like one from a wall at home. That one immediately got me wondering: could I plug in a laptop charger? A small tool charger? A coffee maker?
The answer depends on how much power the device needs. The outlet is handy, but it has a much lower limit than an outlet in your house.
The number to know is 150 watts
I called it a 120-volt outlet when I first noticed it. GMC calls it a 110-volt AC power outlet in the 2015 Sierra owner’s manual. Either way, we’re talking about the household-style plug in the truck.
GMC says the outlet can supply up to 150 watts. That wattage limit is what matters when you’re deciding what to plug in.
A phone charger is one thing. A hair dryer is quite another, even though both have plugs that fit.
The manual also says devices with a high power demand when they first start, including some power tools and compressor refrigerators, may not work. A device can be troublesome even if its ordinary running wattage looks close to the limit.
What would I use it for?
The first things I’d consider are small chargers:
- A phone charger with a normal wall plug
- A camera battery charger
- A modest laptop charger, after checking its power rating
- Another small electronic charger rated well below 150 watts
I’d check the label on the charger before plugging it in. If it lists watts, that gives me a quick comparison with the truck’s 150-watt maximum.
I’d leave some room under that limit, especially if I were charging more than one thing. A power strip wouldn’t give the Sierra more power. Everything plugged into it would still share the same 150-watt limit.
I haven’t tested every device in my truck, so I wouldn’t promise that a particular laptop or charger will work just because it appears on this list. The rating on the device, and whether the outlet stays on when it’s plugged in, are the useful checks.
What I would leave unplugged
I wouldn’t try to run a coffee maker, space heater, hair dryer, or other heating appliance from this outlet. Those generally need far more power than the Sierra supplies.
I’d also be careful with anything that has a motor or compressor. Starting one can take a burst of power beyond what it uses once it’s running. GMC specifically cautions that the outlet isn’t designed for equipment with high initial power demands.
That’s easy to miss. The socket looks like a household outlet, but the truck isn’t supplying household-outlet capacity.
Why does my truck have both this outlet and a cigarette-lighter-style socket?
They serve different purposes.
The household-style outlet supplies AC power for a device with a regular wall plug, as long as that device stays within the outlet’s limits. The round accessory socket supplies 12-volt DC power for equipment designed to plug into a vehicle socket.
The USB port is another separate feature. I had a similar “what is that doing there?” moment when I found the USB port inside my Sierra’s glove box. Finding all three doesn’t mean they’re interchangeable; I’d use the connection meant for the device I’m charging.
For my phone, a suitable USB or 12-volt car charger may be simpler than taking up the AC outlet with a wall charger. For something that only came with a wall plug, the AC outlet could be useful.
What if I plug something in and nothing happens?
I’d start with the easy checks before assuming the outlet is broken.
First, I’d try it with the ignition in ON/RUN. GMC says the outlet’s indicator light comes on when the ignition is in that position, a device drawing less than 150 watts is properly plugged in, and the outlet has no fault.
Then I’d make sure the plug is seated firmly. If I were testing with a laptop charger and got no power, I’d try a small phone wall charger instead. That would help tell me whether the first charger was too demanding or whether the outlet itself needed attention.
GMC says the outlet can shut off if the load exceeds 150 watts or it detects a fault. The manual describes unplugging and reconnecting the device, or cycling retained accessory power, to reset it. I’d remove the device that caused the shutdown before trying again.
If a small, known-working charger still wouldn’t power up with the ignition in ON/RUN, I’d check the owner’s manual for the applicable fuse and have the outlet diagnosed if needed. I wouldn’t keep trying bigger devices to see if one happened to work.
Is it worth using?
For me, yes, as long as I treat it as an outlet for small electronics. Having a place to plug in a charger without buying another adapter is useful in a truck I plan to keep driving.
I just wouldn’t judge its capability by the shape of the socket. Before plugging something unfamiliar into my Sierra, I’d look for its wattage rating, keep it comfortably below 150 watts, and remember that some devices need extra power at startup.
About the author: Daxon Weaver owns the 2015 GMC Sierra 4×4 discussed here. He writes about the features and problems he encounters while using his own vehicles.
