GMC Sierra 1500 collision warning problems

Filed Oct 27, 2026 · Driver assistance · FL

Upon 1st start-up collision warning system light comes on and system is disabled. I shut the truck off immediately and restart it and the collision light goes off and the system functions like normal until the next shut off and restart.

Filed Aug 20, 2026 · Acceleration, Engine · AR

Vehicle: 2026 GMC Sierra 1500 AT4 (3.0L LZ0 Duramax Diesel) Current Mileage: ~16,500 miles Check Engine Light Status: NO Check Engine Light active Description of Incident & Symptoms: •Interstate Incident: While driving at highway speeds, a severe drivetrain vibration occurred (felt like a rear wheel weight flew off). •Dashboard Warnings: Within 5 minutes, intermittent "Traction Control" and "Forward Collision Warning" alerts appeared on the dash, accompanied by a sudden drop in engine power. •Engine Noise & Idle: Once safely pulled over, the engine exhibited a loud mechanical knock and a very rough, unstable idle. •Extended Crank: After shutting the engine off and waiting a few minutes, restarting the truck took roughly twice as long as normal (long crank/delayed start)

Filed Aug 7, 2026 · Acceleration, Driver assistance · TX

Current Unsafe Conditions: Post-Replacement Active Safety Failures. The vehicle presently exhibits two distinct categories of active, ongoing, and dangerous safety failures, both of which were introduced as a direct result of the engine replacement performed by Monument Chevrolet: (a) Severe Drivability Failure. Between approximately 1,500 and 5,000 RPM, the engine repeatedly and without warning lunges forward, drops all power, and lunges again — cycling in this manner between three (3) and six (6) times before stabilizing. This behavior occurs across all gears and driving conditions, which creates a severe and unpredictable hazard particularly when merging into traffic or accelerating onto highways. This failure constitutes an immediate and ongoing risk to the safety of myself and other motorists. (b) Complete ADAS System Failure. The frontal crash response warning light is permanently illuminated on the instrument cluster, rendering the following federally relevant safety systems entirely non-functional: (i) Automatic Emergency Braking / Forward Collision Alert; (ii) Cruise Control; and (iii) Lane Change Assist / Lane Control System. All of these systems were fully operational and properly functioning before the vehicle was submitted for the engine swap. Their failure is an assembly defect introduced by Monument Chevrolet during the course of the repair and constitutes a warranty and safety defect for which General Motors, as the manufacturer and warrantor, bears full responsibility. Medical Hardship and Urgency. This vehicle is my sole personal transportation. It is essential for travel to active medical appointments and upcoming medical procedures. The ongoing failure of General Motors and its authorized service network to restore this vehicle to a safe and fully operable condition has created a serious hardship that directly affects my ability to access needed medical care. Yes, it was driven by a service department supervisor. He did experience the issues.

Filed Jul 15, 2026 · Driver assistance · TX

I purchased this new full-size heavy-duty pickup, and at purchase the selling dealer installed a 3-inch suspension lift kit with 37-inch tires on 22-inch wheels as a paid dealer upfit. The lift kit manufacturer publishes a maximum tire size of 35 inches on a 20-inch wheel for this kit; the tires and wheels the dealer installed exceed that spec. The lift manufacturer confirmed directly that they would never approve exceeding the 35-inch tire / 20-inch wheel recommendation. The dealer's assistant manager confirmed that NO calibrations of any kind were performed after the lift and 37-inch tires were installed, and said nothing is recalibrated when a lift is done with 37-inch tires. This vehicle is factory-equipped with forward collision alert, automatic emergency braking, front pedestrian braking, lane departure warning, and automatic high-beam control. These crash-avoidance systems rely on forward-facing camera and sensor aim, which depends on ride height and suspension geometry. A 3-inch lift with 37-inch tires materially changes that geometry. With no calibration performed, there is no assurance these safety systems are aimed or functioning to spec. The truck was also never aligned after the lift and the tires are cupping. The headlights were never re-aimed for the higher ride height, and the speedometer was never recalibrated and reads inaccurately. The oversized tires also contact the body. The left front tire has torn into the front fender, the fender well is misaligned, and it is forcing the lower front edge of the driver's door out of alignment. The dealer's only proposed remedy is to keep cutting the fender wells; the trimming already done has exposed electrical wiring behind the wheel well to mud, water, and road debris. I am reporting this because the assistant manager's statement suggests it may be the dealer's standing practice—other customers may be driving lifted trucks with uncalibrated crash-avoidance systems without knowing it.

Filed Apr 8, 2026 · Driver assistance · TX

“Service Driver Assist System” message appears every time I turn on my truck. Vehicle would randomly break when driving at slow speeds and show the forward collision alert even if no objects/ car are approaching or being approached. I am concerned about my safety because those sudden hard-breaks could cause an accident.

Filed Mar 10, 2026 · Brakes, Driver assistance · SC

This complaint involves a sudden failure of my vehicle’s Anti-Lock Braking System (ABS) and Forward Collision Warning system, both of which are critical safety systems. While driving my [XXX] son to school, multiple warning lights suddenly appeared on the dashboard without any prior indication of a problem. The vehicle displayed a warning message instructing me not to exceed 36 miles per hour, and several system alerts activated simultaneously, my ABS brake system failed and a transmission failure warning. These issues appeared suddenly while the vehicle was in normal operation. Prior to this incident, the vehicle had been functioning perfectly. The evening before, I had driven the vehicle to pick up my son from wrestling practice with no issues. The following morning, during a routine trip to school, these critical safety warnings appeared without warning. Because the warnings involved the braking system, I immediately took the vehicle to Beach Buick GMC for inspection. The dealership diagnosed the issue as a software failure affecting the braking system and informed me that the vehicle required a software update and system download in order to restore proper operation of the brakes and related safety systems. I was required to pay over $300 for this repair because my vehicle is approximately 3,000 miles outside of the warranty period. However, I believe a failure involving the braking system and safety warnings should not occur suddenly in a properly functioning vehicle and should not be treated as a normal maintenance expense. I contacted **General Motors customer service to ask why a failure involving a critical safety system would not be covered or investigated further. The only explanation provided was that the vehicle was outside of the warranty period. I requested a written explanation of their decision for my records, but I was told that providing written explanations is against company policy. I have more to say but I am out of characters... INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMA

Filed Aug 26, 2025 · Driver assistance, Electrical · FL

On August 15th, 2025, I brought my new 2025 GMC Sierra 1500 Denali to Bill Cramer GM Dealership, 2251 W 23rd St, Panama City, FL 32405, due to a complete loss of audio in the cabin. This affected the turn signals, radio, and critical safety alerts, including collision warnings and seatbelt reminders. Given the vehicle's high cost and its status as a new premium model, this malfunction was both disappointing and alarming, particularly due to its implications for safety. This occurs about every third time I drive the vehicle. The dealership retained my vehicle for over a week to diagnose and address the issue. I received an email stating that the service was complete and the truck was ready for pickup. However, upon arrival, a service technician informed me that they could not identify the cause of the audio failure and, consequently, no repairs were made. I was told the dealership would continue consulting with General Motors' corporate engineers to determine the cause and solution.

Filed Jul 12, 2025 · Driver assistance · CA

1. Lane Keeping Assistantance: The green vehicle indicator on the dashboard will disappear and stay off while driving. When it is off, it is unsafe. 2. Parking Collision Warning: The front and back sensors will disappear and become nonfunctional while driving and parking. Sometimes they activate for no reason as well. 3. Both exterior mirrors: After starting the engine to drive off , both exterior mirrors will lower automatically from my setting. After the truck is started and driven off, they must be rest again.

Filed Jun 25, 2025 · Driver assistance, Engine · 20,000 miles · VA

The contact owns a 2024 GMC Sierra 1500. The contact stated while driving 45 MPH, the low fuel warning light, the forward collision avoidance warning light, the check engine warning light and other unknown warning lights were illuminated. The message "Steering Assist Reduced" was displayed. The contact stated that the vehicle lost motive power. The contact was able to pull to the side of the road. The vehicle failed to restart and was towed to the dealer to be diagnosed, but the dealer could not determine the cause of the failure. The contact stated that the failure recurred while driving. The vehicle was towed to the dealer, where it was being diagnosed. The vehicle was not diagnosed or repaired. The contact related the failure to the federal safety agency Action Number: PE25001(Engine, Engine and Engine Cooling) and the federal safety agency Campaign Number: 25V274000(Engine and Engine Cooling). The manufacturer was notified of the failure and referred the contact to the federal safety agency Hotline for assistance. The failure mileage was approximately 20,000.

Filed May 13, 2025 · Driver assistance, Electrical · OR

Intermittent failure of audio and safety alerts (Forward Collision Alert, Lane Departure Warning) Dealership’s response: “No fix” despite warranty. Safety impact: Increased collision risk.