2021 GMC Sierra 1500 Reliability Report

Nearly all of these complaints concern the 6.2-liter engine recall. Many owners received the notice but were told repair parts were unavailable. Some trucks failed the inspection and sat at the dealer for more than two months waiting on a new engine. Where the remedy was performed, it consisted of thicker oil, a new oil cap and filter, and a manual update, and owners doubt it fixes the defect. Some also report fuel economy dropping. Actual failures include heavy shaking, a check engine light, and sudden loss of power, several around 60,000 miles.

Power steering assist cuts out suddenly. A Service Power Steering or reduced steering assist warning usually appears, often together with ESC and parking brake alerts, and steering becomes heavy or locks. Dealers report binding steering racks, backordered parts, and one repair quote of $5,000. Engine shutdowns at speed also take away steering and brake assist. Front suspension failures cause the worst outcomes: ball joints separate from control arms and alignment cam pins shear, and one of these failures ended in a crash. One report describes a steering shaft bolt missing, leaving the wheel spinning freely.

This mixed group repeats patterns found elsewhere. Engines lose all power while driving, with a slipped timing chain and piston rod failure among the diagnoses. Coolant control valves fail, sometimes more than once, causing constant fan operation, swinging temperatures, or reduced power, and parts are backordered. The tailgate opens by itself, including while driving. Other reports cover a power running board retracting while someone stood on it, a leaking rear sliding window frame, exhaust fumes in the cabin, and a surround-view camera misjudging distance in a parking collision.

Brakes fail without warning in several reports. A brake failure message appears, the pedal sinks to the floor, and one truck rear-ended another car in slow traffic. Dealers fixed these trucks by replacing the master cylinder, and in one case the brake booster too, on trucks showing between 21,539 and 22,500 miles. The electronic parking brake drags or applies on its own, wearing inner pads and rotors early and sometimes braking the truck hard at highway speed, even after a recall repair. Trailer brake controller disconnects also come up repeatedly.

Most of these complaints involve the power multi-function tailgate. The inner gate drops or the whole tailgate opens by itself, while parked and in rain, and it damaged cargo equipment in one case. Owners note that a related recall covers heavier-duty Sierras but not their trucks, so repairs are not covered. Water leaks through the rear sliding window, and the dealer charges for the fix. One report describes a fractured front frame found after the truck shook violently and lost power at about 30,000 miles.

The electronic tailgate unlatches and opens by itself, both while parked and while driving. In one case luggage fell onto the road. The failure tends to repeat, sometimes after a warranty repair to the tailgate switch, and dealers often cannot find a cause. Water gets past worn tailgate buttons and leaves them dead. Owners say their trucks were left out of the tailgate recall. Reported failures cluster between about 41,000 and 76,000 miles.

A Service Safety Restraint System warning flashes on and off, sometimes every few seconds. It shows up very early, on trucks with fewer than 2,000 or 5,600 miles. One dealer said the truck was unsafe to drive because the airbags might not deploy. Two crash reports describe airbags failing to deploy in collisions severe enough to total the truck. In one of those crashes, smoke filled the cabin and the driver was injured.