Launch year of the new truck — same DFM lifter risk as the Silverado, plus a couple of Sierra-only quirks to check.

GM ran a Customer Satisfaction Program for 2019 trucks covering engine oil-cooler (EOC) lines that leak and detach at the crimp joints — worse in cold weather. A Sierra Denali owner in the file describes it exactly: 'Turn off engine, no oil pressure' at 30 mph, the dealer finding the oil-cooler line detached at 77,000 miles. Continued driving after a detachment risks loss of propulsion and engine damage. The remedy replaces the lines, oil, and filter. Some owners find their VIN isn't included and pay out of pocket — confirm eligibility and whether the work was done.

GM's Customer Satisfaction Program N182190821 covers a power steering belt that "may slip due to tooth wear-out or poor belt tooth-to-gear tooth fit," and the program is blunt about the consequence: "Power steering assist may be reduced or lost intermittently, if early warning signs are ignored." GM names those warning signs, which makes this an unusually checkable item — a "Steering Assist is Reduced" message, audible clicking or squealing, or a change in steering effort. The remedy is to inspect and if necessary replace the steering gear assembly. Turn the wheel lock to lock at idle and listen; any of the three signs is reason to have the program checked by VIN before you buy.

Not every truck this year got the 8-speed. On trucks with the 6-speed automatic, GM ran a Customer Satisfaction Program for "a slight deformation in the stator shaft" that leaves drivers with "vibration and a decrease in shift performance" — and the remedy is to replace the transmission. If the truck you are looking at has the 6-speed, that is potentially a free transmission on an affected VIN, which is worth establishing before you talk price. Test-drive for vibration under load and for lazy or uneven shifts, and check the program by VIN.

The Sierra's signature feature is the MultiPro multi-function powered tailgate — and a 2019 owner reported it slamming open rather than lowering gently, striking a child in the chest, both from the key fob and the dash button. It's a GMC-exclusive item not found on the Silverado, and there's no recall. On any Sierra with the powered tailgate, exercise every tailgate function and watch for abrupt, uncontrolled motion.

Two launch-year clusters. The power sliding rear window (2019–2022 crew cabs) can leak where the sliding pane meets the frame, wetting the headliner and killing the backup camera. And a wave of remote-start electronic-brake-control failures throws 'Brake System Failure 62 mph top speed / Service ESC / reduced steering assist' — addressed by EBCM software recalls 19V889 and 20V055 (both free). Several fire/stall recalls (battery cable 19V888, driveshaft 20V650, pretensioner 19V814) round out the year. Check the rear headliner for staining and confirm every recall by VIN. Separate from the leaks, GM also documented “areas of high electrical resistance on the rear defroster circuit” on trucks with the power sliding rear window — heat that “could melt the areas surrounding the circuit” and, rarely, “cause a non-propagating fire.” The Customer Satisfaction Program covers the buss bar and contact covers, plus the glass where it is already damaged, and its stated scope runs 2014 through 2019. Run the defroster and cycle the window while watching for anything that smells hot.

The 2019 trucks pair some engines with the 8-speed automatic, which carries the same shudder and hard 1–2 shift the third generation was known for — enough to feed a class action on 2019–2020 models. Sierra owners report it 'shakes at all speeds' with hard shifts that 'chirp the rear tires.' The 10-speed on other trims is much better. Test-drive for shudder and prefer the 10-speed or a documented fluid service.