2021 GMC Sierra gets Jack-Knife Alert tech, Black Diamond Edition trim

GMC's workhorse pickup trucks are being treated to loads of fresh trailer towing aides, plus an even showier new HD Denali trim for 2021.

Emme Hall Former editor for CNET Cars
I love two-seater, RWD convertibles and own a 2004 Mazdaspeed Miata for pavement fun and a lifted 2001 Miata for pre-running. I race air-cooled Volkswagens in desert races like the Mint 400 and the Baja 1000. I have won the Rebelle Rally, seven-day navigational challenge, twice and I am the only driver to compete in an EV, the Rivian R1T.
Emme Hall
3 min read
2021 GMC Sierra Denali Heavy Duty Black Diamond Edition
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2021 GMC Sierra Denali Heavy Duty Black Diamond Edition

The GMC Sierra Heavy Duty is a particularly imposing presence in its new Denali Black Diamond Edition trim. 


aims to deliver the best-towing pickup truck on the market, and it's already rolled out myriad cameras and sensors to make tough jobs easier for its customers. Now, the 2021 GMC Sierra full-size pickup will get added trailer tech for even greater convenience and safety in both light-duty and heavy-duty model trims. It's also stacking the deck with a new 2021 GMC Sierra HD Denali Black Diamond Edition trim that offers even more bling than usual.

GMC's new Jack-Knife Alert can warn with a visual alert and a quick vibration to the driver's seat bottom when their trailer is at risk for getting out-of-sorts. Jackknifing occurs when the trailer gets out of sync with the towing vehicle's trajectory and the trailer starts to come around, forming an L or a V shape. This usually happens because the trailer tires have lost traction, but trailers can also jackknife when backing up, too. By using cameras and sensors, the Sierra can sense a potential jackknife situation and warn the driver of impending problems. The tech cannot, however, correct such developing situations on its own. Depending on the severity, drivers may be able to recover the trailer by easing up on the gas or steering into the skid. 

Also new is Trailer Length Indicator, a system that works as an enhanced blind-spot monitor. When a driver activates a properly equipped 2021 Sierra's turn signal, a red overlay is displayed on the infotainment screen's camera feed, visually extending twice the length of the trailer. This helps drivers see if a vehicle is in (or approaching) its "red zone," enabling safer lane changes.

2021 GMC Sierra
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2021 GMC Sierra

Don't jackknife that trailer!


Other improved trailer tech helps drivers back up their vehicles more easily, with new guide lines on the main infotainment display. The rear side-view function, which previously only worked when moving forward on 2020 models, will henceforth also work in reverse for 2021 Sierras. To help with hitching up, a new Trailer-Angle Indicator feature comes on the scene, as does a Cargo Bed View enhancement feature and Bed Hitch Guidance for gooseneck or fifth-wheel trailers. 

On the light-duty Sierra 1500, all this technology is part of an optional Technology Package. On Heavy Duty models, the tech is standard on the luxurious Denali trim, but SLT and AT4 drivers will need to option their trucks with HD Surround Vision with Two Trailer Cameras, as well as the Bed View Camera system to get all the new goodies.

As for other updates, drivers of the can now get the super-cool MultiPro tailgate on SLE and Elevation trims. The AT4 will have 20-inch Goodyear Wrangler Territory tires available and a high-clearance step to help entrance and egress. 

Further, the 3.0-liter Duramax turbodiesel engine gets a substantial price cut of $1,500. For 2021, on SLT, AT4 and Denali trims the diesel will cost just $995 more than the 5.3-liter V8 offering. On the SLE and Elevation, the price cut brings the price premium down to $2,390.

2021 GMC Sierra: New trailer tech, Denali Black Diamond trim on tap

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As for the Sierra Heavy Duty, the MultiPro tailgate will be standard on the SLE trim and the AT4 will have available 18-inch mud-terrain tires and a high-clearance step. The trim will get a 360-degree camera, as well as a bed-view camera standard. 

Those who opt for the new super-fancy Black Diamond Edition trim seen above will get 20-inch high-gloss black wheels and power-retractable side steps on their already less-than-subtle Denali.

No word on full model pricing or availability yet, but we expect to see the 2021 GMC Sierra 1500 and Heavy Duty models in dealerships this fall. With all those cameras and chrome, they're going to be hard to miss.