2021 Chevrolet Tahoe engine problems

“Driving on the highway when all lights lit up on the dashboard. Car slowed down immediately following alert notifications. Towed to dealer. Was told I needed Camshaft and both banks of lifters all head bolts and head gaskets (W) [Other]: Camshaft actuator and bolt and chain tensioner”

“Vehicle is a 2021 Chevrolet Tahoe Premier with under 50,000 miles. The vehicle experienced a sudden and complete loss of reverse gear, accompanied by violent lurching, sputtering, and dangerous hesitation/stuttering while accelerating between gears at speed. A certified dealership inspection physically diagnosed the vehicle with multiple stuck valves inside the transmission control valve body, requiring a complete valve body replacement. This exact mechanical failure completely mirrors the known safety defects outlined in GM Special Coverage Program N242454441, which details transmission pressure losses causing gear engagement conflicts and potential rear-wheel lock-up hazards. The replacement transmission component installed by the certified dealer failed catastrophically within four miles of pickup, again causing severe transmission sputtering and shifting failures that render the vehicle entirely unroadworthy and a safety hazard on public roads. The dealership has been forced to order an entirely new replacement valve body assembly under warranty due to a consecutive failure. General Motors Corporate Customer Assistance acknowledged that the vehicle is…”

“The vehicle suffered complete internal engine failure due to a snapped timing chain on startup. The vehicle turned over via the starter motor but failed to start. A professional diagnosis confirmed the broken timing chain caused extensive valve-to-piston damage, requiring a full engine replacement. This failure appears to be a direct consequence of the known 6.2L L87 V8 engine crankshaft and connecting rod manufacturing defects. Severe mechanical resistance or violent rotational harmonics at the crankshaft level place un-engineered stress on the timing drive system, causing the chain to snap under startup torque. All broken components are preserved and available for inspection. The defect creates a severe risk of sudden, total loss of propulsion while driving. Had the compromised timing chain snapped at highway speeds rather than on startup, it would cause immediate engine seizure, a sudden loss of power steering, and a loss of power brake vacuum assist. This leaves the driver unable to accelerate or safely steer out of active traffic, creating an extreme risk of a high-speed crash.The broken timing chain and total engine destruction were officially diagnosed…”

“On [XXX], while driving near Mammoth Mountain, California (Highway [XXX]), the vehicle suffered a sudden, severe engine malfunction. The engine began misfiring violently, accompanied by a loud, mechanical clacking noise, and experienced an immediate loss of propulsion power. This mechanical failure left my family—including young children—completely stranded on the side of a mountain highway in a secluded wilderness area with dropping temperatures (39°F) and active local wildlife Because the vehicle could not safely maintain highway speeds or generate sufficient power, it created an immediate and severe traffic safety hazard, forcing us to secure emergency transport for the vehicle. Which took 4hours for someone to come out to the secluded hwy on a holiday weekend. Dealership Diagnostic Findings A formal inspection conducted by a certified General Motors dealership (Michael Hohl Motor Company) confirmed the following: Symptoms: Gas engine diagnostic confirmed "Misfire, and clacking noises coming from passenger side of the motor." Diagnosis: Cylinder Head / Valve / Lifter / Lash Adjuster failure. The dealership documented a collapsed lifter and recommended a…”

“2021 Chevrolet Tahoe – Unexpected Shutdown/Restart While Stopped On two separate occasions, my 2021 Chevrolet Tahoe has unexpectedly appeared to shut down while I was stopped with my foot on the brake. The vehicle is equipped with Auto Stop/Start, and initially the event seems like a normal Auto Stop. However, instead of a normal engine Auto Stop/Start cycle, the vehicle appears to shut down or reset more completely. The event is jarring, and the power door locks lock/unlock as the vehicle shuts down and restarts. The vehicle subsequently restarts and I have been able to continue driving. This has now occurred twice while stopped. I am concerned that the vehicle may be experiencing an unintended stall, loss of electrical power, or another malfunction rather than normal Auto Stop/Start operation. I checked my VIN through NHTSA and it does not currently show an open recall. I am aware that certain 2021 Chevrolet Tahoes have previously been recalled for a condition that could result in an engine stall, although my VIN does not appear to be included in that recall population.”

“The number 7 DFM lifter failed and is suspected of failing due to the Active Fuel System. The vehicle is currently at the dealership where it was diagnosed and is awaiting replacement parts that are on GMC back order for a month or longer. The vehicle started shaking on 8/25/26 when idle and the following warning lights were visible: AVS, traction control, and ECU.”