High Severity Issue
This component has been associated with crashes, fires, or deaths.
This Problem Across All Years
I was driving and a message popped up "Service Traction Control", then another message popped up "Forward Collision System Unavailable". Then the car started making this knocking sound and every time I would try and accelerate there would be a loud sound and almost a pulling stopping it from picking up much speed. I took the car into the dealer/repair shop and they said it was an issue with the lifters that had to be replaced and potentially an issue with the cam. They said this repair would cost upwards of $6,000 and I have never had this issue with the car before. This came out of nowhere and the car had not been showing any signs of this occurring before. This is a 2021 GMC Yukon and I drive my Wife and three sons in that car daily.
I was driving and a message popped up "Service Traction Control", then another message popped up "Forward Collision System Unavailable". Then the car started making this knocking sound and every time I would try and accelerate there would be a loud sound and almost a pulling stopping it from picking up much speed. I took the car into the dealer/repair shop and they said it was an issue with the lifters that had to be replaced and potentially an issue with the cam. They said this repair would cost upwards of $6,000 and I have never had this issue with the car before. This came out of nowhere and the car had not been showing any signs of this occurring before. This is a 2021 GMC Yukon and I drive my Wife and three sons in that car daily.
traction control system ESC system Suddenly and without warning, multiple warning lights started flashing including check engine. The vehicle lost power and traction. There was a loud knocking and metallic whining sound. The vehicle began to vibrate and struggled to move forward and felt like the wheels were slipping. The loss of these functions was alarming because it was dark, we were in a construction zone, and my 15-year old daughter was driving having recently earned her driver's permit. The car following us almost rear ended us. It was such an abrupt engine failure it scared me and my daughter.
traction control system ESC system Suddenly and without warning, multiple warning lights started flashing including check engine. The vehicle lost power and traction. There was a loud knocking and metallic whining sound. The vehicle began to vibrate and struggled to move forward and felt like the wheels were slipping. The loss of these functions was alarming because it was dark, we were in a construction zone, and my 15-year old daughter was driving having recently earned her driver's permit. The car following us almost rear ended us. It was such an abrupt engine failure it scared me and my daughter.
Vehicle: 2021 GMC Denali Mileage: ~48,000 miles Purchase Price: $62,000 Issue: Airbags & crash sensors failed to deploy Complaint Text: I am filing a safety complaint regarding my 2021 GMC Denali. I was involved in a rear-end collision at approximately 45 mph, where I struck another vehicle straight on from behind. The impact was severe enough to total my vehicle, yet no airbags deployed, and no forward collision warning or crash sensor systems activated. This is especially concerning because this vehicle was previously involved in a front-end collision (not my fault) and underwent extensive repairs. I was assured all systems were repaired and functioning properly. Additionally, my vehicle had completed recall work related to safety systems prior to this crash. This is the second front-end crash involving this vehicle where airbags failed to deploy. Given the speed and severity of the impact, airbags should have deployed. The failure of these systems placed my life at serious risk. The vehicle has since been totaled and taken by insurance, but I am requesting that this failure be formally investigated as a potential safety defect in the airbag and sensor systems. I am extremely concerned that the vehicle’s safety systems were either defective or not properly restored following repairs and recalls.
Vehicle: 2021 GMC Denali Mileage: ~48,000 miles Purchase Price: $62,000 Issue: Airbags & crash sensors failed to deploy Complaint Text: I am filing a safety complaint regarding my 2021 GMC Denali. I was involved in a rear-end collision at approximately 45 mph, where I struck another vehicle straight on from behind. The impact was severe enough to total my vehicle, yet no airbags deployed, and no forward collision warning or crash sensor systems activated. This is especially concerning because this vehicle was previously involved in a front-end collision (not my fault) and underwent extensive repairs. I was assured all systems were repaired and functioning properly. Additionally, my vehicle had completed recall work related to safety systems prior to this crash. This is the second front-end crash involving this vehicle where airbags failed to deploy. Given the speed and severity of the impact, airbags should have deployed. The failure of these systems placed my life at serious risk. The vehicle has since been totaled and taken by insurance, but I am requesting that this failure be formally investigated as a potential safety defect in the airbag and sensor systems. I am extremely concerned that the vehicle’s safety systems were either defective or not properly restored following repairs and recalls.
While driving vehicle on 11/08/2025, vehicle made a popping noise and loss power. We were out of town and had to pay out of pocket to have vehicle towed to a dealership and hour away from our home. Dealership diagnosed issue with engine failure due to lifter fell and caused damage to cam shaft and bore. I will be without a vehicle for an additional 2 to 4 weeks waiting on a back ordered engine from GM, and continue making payments on vehicle as well. This issue seems to be an ongoing problem that GM is ignoring…….GM should compensate towing, car rental, and repair/ replacement charges due to failure.
While driving vehicle on 11/08/2025, vehicle made a popping noise and loss power. We were out of town and had to pay out of pocket to have vehicle towed to a dealership and hour away from our home. Dealership diagnosed issue with engine failure due to lifter fell and caused damage to cam shaft and bore. I will be without a vehicle for an additional 2 to 4 weeks waiting on a back ordered engine from GM, and continue making payments on vehicle as well. This issue seems to be an ongoing problem that GM is ignoring…….GM should compensate towing, car rental, and repair/ replacement charges due to failure.
The contact owns a 2021 GMC Yukon. The contact stated that while driving at various speeds, the Forward Collision Avoidance system erroneously activated, causing the vehicle to suddenly slow down. The vehicle was taken to the local dealer who serviced the Forward Collision Avoidance system camera and sensors. No further information was available. Additionally, while driving at highway speeds, there was a knocking sound coming from the engine compartment, and the seat restraint failure message was displayed. The cause of the failure was not yet determined. The manufacturer was notified of the failure. The failure mileage was 20,000.
The contact owns a 2021 GMC Yukon. The contact stated that while driving at various speeds, the Forward Collision Avoidance system erroneously activated, causing the vehicle to suddenly slow down. The vehicle was taken to the local dealer who serviced the Forward Collision Avoidance system camera and sensors. No further information was available. Additionally, while driving at highway speeds, there was a knocking sound coming from the engine compartment, and the seat restraint failure message was displayed. The cause of the failure was not yet determined. The manufacturer was notified of the failure. The failure mileage was 20,000.
The component that failed was the Camshaft and Lifters in the Engine - My safety and others was put at risk because while going 45mph, I suddenly lost forward moving power and couldn't go faster than 35 - braking power was sketchy and only responsive when pumped. - I received the following errors on my dash "Service ESC" "Service Traction Control", Reduced Acceleration Drive with Care", "Forward Collision System Unavailable", "Service Emission System" the vehicle would shudder violently- this problem has been confirmed and corrected at a huge expense (see bill) -
The component that failed was the Camshaft and Lifters in the Engine - My safety and others was put at risk because while going 45mph, I suddenly lost forward moving power and couldn't go faster than 35 - braking power was sketchy and only responsive when pumped. - I received the following errors on my dash "Service ESC" "Service Traction Control", Reduced Acceleration Drive with Care", "Forward Collision System Unavailable", "Service Emission System" the vehicle would shudder violently- this problem has been confirmed and corrected at a huge expense (see bill) -
Font Camera failure. Front camera controls many "safety features" which fail without the camera. Vehicle under mileage warranty amount but not under time warranty ( 3 years ). Camera only covered under bumper to bumper.
Font Camera failure. Front camera controls many "safety features" which fail without the camera. Vehicle under mileage warranty amount but not under time warranty ( 3 years ). Camera only covered under bumper to bumper.
My vehicle has software that controls the rear gate, cameras, and my safety features for blind spots—seat buzzer to warn of collisions and voice activated phone system. I recently had a safety recall involving my back wheels locking up during driving. I had the recall done by Power Chevrolet and it affected my cameras, which I noticed were longer accurate immediately after leaving the dealership. My seat buzzer kept buzzing warning me of a collision due to the cameras inaccuracy. I am unsure if it affected my blind spot warning but my car was unsafe to drive as the safety features fill in many blind spots in this big vehicle. Additionally I had been having issues with my back gate opening when it should not resulting in two stops to close it— one in Costco and one on [XXX] outside of Philomath, Oregon. These are safety issues. To get the software issues resolved, it cost an additional $210 for the updates and my back gate is still not fixed and no solution is offered. My fear is that people will be unaware their cameras or safety features are no longer properly calibrated and hit something or even worse, be unable to pay for software updates to make these features functional resulting in more crashes. I was unaware of the software updates ( I did all updates GMC pushed) needed to be done and this just continues on with more software updates to be released requiring future payments. I bought this car new and this was not disclosed or even discussed. GMC can push down updates that make other updates necessary and be an unending source of revenue for them. Oregon just passed a right to repair law but cars are exempt. This will result in unsafe vehicles on the road. My oil change cost me $350 with $210 the software updates. What were these safety related updates not done as recalls? INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
My vehicle has software that controls the rear gate, cameras, and my safety features for blind spots—seat buzzer to warn of collisions and voice activated phone system. I recently had a safety recall involving my back wheels locking up during driving. I had the recall done by Power Chevrolet and it affected my cameras, which I noticed were longer accurate immediately after leaving the dealership. My seat buzzer kept buzzing warning me of a collision due to the cameras inaccuracy. I am unsure if it affected my blind spot warning but my car was unsafe to drive as the safety features fill in many blind spots in this big vehicle. Additionally I had been having issues with my back gate opening when it should not resulting in two stops to close it— one in Costco and one on [XXX] outside of Philomath, Oregon. These are safety issues. To get the software issues resolved, it cost an additional $210 for the updates and my back gate is still not fixed and no solution is offered. My fear is that people will be unaware their cameras or safety features are no longer properly calibrated and hit something or even worse, be unable to pay for software updates to make these features functional resulting in more crashes. I was unaware of the software updates ( I did all updates GMC pushed) needed to be done and this just continues on with more software updates to be released requiring future payments. I bought this car new and this was not disclosed or even discussed. GMC can push down updates that make other updates necessary and be an unending source of revenue for them. Oregon just passed a right to repair law but cars are exempt. This will result in unsafe vehicles on the road. My oil change cost me $350 with $210 the software updates. What were these safety related updates not done as recalls? INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Upon cold start vehicle rattles when idling down and growling noise when accelerating upon left or right turns. Also, has constant vibrations with sound of metal rattling at speeds above 30 mph. Forward collision light on without a significant amount of mileage on vehicle. I have taken my vehicle to dealership at least 5 times referencing the vibrations. Growling noise was heard by service advisor last visit October 2024, and he stated it probably were the tires. I advised him that brand new tires were put on vehicle, April 18th 2024, rear vibration has never stopped from time of purchase. I have asked dealership to check drivetrain as it is a know issue for 21 Yukon Denali. Vehicle has not received recall but was manufactured at Arlington plant where the parts of the drive shaft was not properly heated and differential is known for issue upon cold start. Vehicle powertrain warranty is due to expire August 2025 or 60,045 mileage. Therefore with that, the vehicle was placed in service August 2020 months before unproperly heated driveshaft recall was determined. My vehicle should be on the list for this recall as GMC noted this to have occurred on vehicle prior to 07/2021. In addition, a chirping noise comes from front of vehicle while idling and when automatic stop starts back up.There are already known recalls for two of issues noted above.
Upon cold start vehicle rattles when idling down and growling noise when accelerating upon left or right turns. Also, has constant vibrations with sound of metal rattling at speeds above 30 mph. Forward collision light on without a significant amount of mileage on vehicle. I have taken my vehicle to dealership at least 5 times referencing the vibrations. Growling noise was heard by service advisor last visit October 2024, and he stated it probably were the tires. I advised him that brand new tires were put on vehicle, April 18th 2024, rear vibration has never stopped from time of purchase. I have asked dealership to check drivetrain as it is a know issue for 21 Yukon Denali. Vehicle has not received recall but was manufactured at Arlington plant where the parts of the drive shaft was not properly heated and differential is known for issue upon cold start. Vehicle powertrain warranty is due to expire August 2025 or 60,045 mileage. Therefore with that, the vehicle was placed in service August 2020 months before unproperly heated driveshaft recall was determined. My vehicle should be on the list for this recall as GMC noted this to have occurred on vehicle prior to 07/2021. In addition, a chirping noise comes from front of vehicle while idling and when automatic stop starts back up.There are already known recalls for two of issues noted above.
On 4-5 occasions since purchasing a new 2021 GMC Yukon Denali the automatic breaking function has engaged for no reason, with no obstruction in the roadway. It has occurred at low speed (after disengaging break and starting to drive). Obviously, this is a major safety issue.
On 4-5 occasions since purchasing a new 2021 GMC Yukon Denali the automatic breaking function has engaged for no reason, with no obstruction in the roadway. It has occurred at low speed (after disengaging break and starting to drive). Obviously, this is a major safety issue.
20221 GMC Yukon Denali Suddenly comes to a stop ,” it brakes hard “ It acts like when you are almost gonna hit someone and brakes engage so hard. Jerks everyone to the front !no other lights coming on or anything else! For now it’s been doing it at slow speed , really don’t wanna experience it at a high speed , pls help these vehicles are so expensive to be dealing with this . This is my wife and kids vehicle
20221 GMC Yukon Denali Suddenly comes to a stop ,” it brakes hard “ It acts like when you are almost gonna hit someone and brakes engage so hard. Jerks everyone to the front !no other lights coming on or anything else! For now it’s been doing it at slow speed , really don’t wanna experience it at a high speed , pls help these vehicles are so expensive to be dealing with this . This is my wife and kids vehicle
2 different times I have been driving once at a high speed of 70 on the highway and then driving 15-20 miles an hour today my automatic braking engaged and threw me forward which is a very scary feeling. I have not taken it in for service for that as it had only happened once a few months ago and there have been no warning lamps indicating an issue.
2 different times I have been driving once at a high speed of 70 on the highway and then driving 15-20 miles an hour today my automatic braking engaged and threw me forward which is a very scary feeling. I have not taken it in for service for that as it had only happened once a few months ago and there have been no warning lamps indicating an issue.
I was driving on the interstate on a low speed and my SUV came to a complete stop with no notice. Nothing was in the road or close in front of me. Jerked me to the front and seat belt left a red spot on my neck from the seat belt, scared the crap out of me. I thought I was hit from behind. The is a hug safety concern that needs to be recalled and fixed immediately before it causes an accident.
I was driving on the interstate on a low speed and my SUV came to a complete stop with no notice. Nothing was in the road or close in front of me. Jerked me to the front and seat belt left a red spot on my neck from the seat belt, scared the crap out of me. I thought I was hit from behind. The is a hug safety concern that needs to be recalled and fixed immediately before it causes an accident.
I was involved in a vehicle accident on 10/6/2021 where my vehicle was stuck by an uninsured motorist driving recklessly on the interstate causing a total of 4 car collision. My vehicle was a a 2021 GMC YUKON SLT SUV, in which I was struck on rear drivers side quarter panel and again by another vehicle in the front bumper by another vehicle that struck in the rear bumper by the reckless driver. With my vehicle being struck by two vehicles I was shocked to learn the Onstar safety security features did not detect or contact me regarding the accident. It wasn’t until the wrecker driver arrived to pull my vehicle onto the tow truck that I received a diagnosis notification email from o star about my antilock braking system. Although I was wearing my seat belt, the impact of the collision was very shocking, my chest and neck struck the steering wheel, my glasses were knocked completely off my face on to the passenger side floor board, my personal belongings in the passenger seat, were thrown and scattered over the passenger floor area. Once the emergency authorities were on the scene everything was about over I contacted Onstar via phone, and asked why wasn’t I contacted or my accident detected, and the call taker/on star representative advised me because my airbags wasn’t deployed, they did not receive a notification or alert regarding my emergency. I have attempted to make contact with Onstar several times since the accident and as of today I have yet to get an answer of why my air bags did deploy and why the emergency sensors did detect the impact notify emergency services as this is a feature that i was charged for monthly and added protection that I counted on to assist me but very much failed me at my time of need.
I was involved in a vehicle accident on 10/6/2021 where my vehicle was stuck by an uninsured motorist driving recklessly on the interstate causing a total of 4 car collision. My vehicle was a a 2021 GMC YUKON SLT SUV, in which I was struck on rear drivers side quarter panel and again by another vehicle in the front bumper by another vehicle that struck in the rear bumper by the reckless driver. With my vehicle being struck by two vehicles I was shocked to learn the Onstar safety security features did not detect or contact me regarding the accident. It wasn’t until the wrecker driver arrived to pull my vehicle onto the tow truck that I received a diagnosis notification email from o star about my antilock braking system. Although I was wearing my seat belt, the impact of the collision was very shocking, my chest and neck struck the steering wheel, my glasses were knocked completely off my face on to the passenger side floor board, my personal belongings in the passenger seat, were thrown and scattered over the passenger floor area. Once the emergency authorities were on the scene everything was about over I contacted Onstar via phone, and asked why wasn’t I contacted or my accident detected, and the call taker/on star representative advised me because my airbags wasn’t deployed, they did not receive a notification or alert regarding my emergency. I have attempted to make contact with Onstar several times since the accident and as of today I have yet to get an answer of why my air bags did deploy and why the emergency sensors did detect the impact notify emergency services as this is a feature that i was charged for monthly and added protection that I counted on to assist me but very much failed me at my time of need.
I was involved in a vehicle accident on 10/6/2021 where my vehicle was stuck by an uninsured motorist driving recklessly on the interstate causing a total of 4 car collision. My vehicle was a a 2021 GMC YUKON SLT SUV, in which I was struck on rear drivers side quarter panel and again by another vehicle in the front bumper by another vehicle that struck in the rear bumper by the reckless driver. With my vehicle being struck by two vehicles I was shocked to learn the Onstar safety security features did not detect or contact me regarding the accident. It wasn’t until the wrecker driver arrived to pull my vehicle onto the tow truck that I received a diagnosis notification email from o star about my antilock braking system. Although I was wearing my seat belt, the impact of the collision was very shocking, my chest and neck struck the steering wheel, my glasses were knocked completely off my face on to the passenger side floor board, my personal belongings in the passenger seat, were thrown and scattered over the passenger floor area. Once the emergency authorities were on the scene everything was about over I contacted Onstar via phone, and asked why wasn’t I contacted or my accident detected, and the call taker/on star representative advised me because my airbags wasn’t deployed, they did not receive a notification or alert regarding my emergency. I have attempted to make contact with Onstar several times since the accident and as of today I have yet to get an answer of why my air bags did deploy and why the emergency sensors did detect the impact notify emergency services as this is a feature that i was charged for monthly and added protection that I counted on to assist me but very much failed me at my time of need.
I was involved in a vehicle accident on 10/6/2021 where my vehicle was stuck by an uninsured motorist driving recklessly on the interstate causing a total of 4 car collision. My vehicle was a a 2021 GMC YUKON SLT SUV, in which I was struck on rear drivers side quarter panel and again by another vehicle in the front bumper by another vehicle that struck in the rear bumper by the reckless driver. With my vehicle being struck by two vehicles I was shocked to learn the Onstar safety security features did not detect or contact me regarding the accident. It wasn’t until the wrecker driver arrived to pull my vehicle onto the tow truck that I received a diagnosis notification email from o star about my antilock braking system. Although I was wearing my seat belt, the impact of the collision was very shocking, my chest and neck struck the steering wheel, my glasses were knocked completely off my face on to the passenger side floor board, my personal belongings in the passenger seat, were thrown and scattered over the passenger floor area. Once the emergency authorities were on the scene everything was about over I contacted Onstar via phone, and asked why wasn’t I contacted or my accident detected, and the call taker/on star representative advised me because my airbags wasn’t deployed, they did not receive a notification or alert regarding my emergency. I have attempted to make contact with Onstar several times since the accident and as of today I have yet to get an answer of why my air bags did deploy and why the emergency sensors did detect the impact notify emergency services as this is a feature that i was charged for monthly and added protection that I counted on to assist me but very much failed me at my time of need.
I had just left the house driving through my neighborhood at about 35 MPH when for no reason the emergency braking engaged. The road was deserted, no other vehicles, pedestrians, dogs or objects in roadway. There was a momentary red dash alert, but I didn't have time to read it.
I had just left the house driving through my neighborhood at about 35 MPH when for no reason the emergency braking engaged. The road was deserted, no other vehicles, pedestrians, dogs or objects in roadway. There was a momentary red dash alert, but I didn't have time to read it.
I had just left the house driving through my neighborhood at about 35 MPH when for no reason the emergency braking engaged. The road was deserted, no other vehicles, pedestrians, dogs or objects in roadway. There was a momentary red dash alert, but I didn't have time to read it.
I had just left the house driving through my neighborhood at about 35 MPH when for no reason the emergency braking engaged. The road was deserted, no other vehicles, pedestrians, dogs or objects in roadway. There was a momentary red dash alert, but I didn't have time to read it.
This new 2021 GMC Yukon Denali we purchased on June 2, 2021 has a very sophisticated controls system that includes a feature, entitled "Brake Assist," that is designed to detect "rapid brake pedal applications due to emergency braking situations and provides additional braking to activate the Antilock Brake System (ABS) if the brake pedal is not pushed hard enough to activate ABS normally." "Brake Assist disengages when the brake pedal is released." After I left the dealership (June 2nd), I noticed that the "Service Brake Assist" light had illuminated on the Driver Information Center (DIC). I pulled off the road to check the Owner's Manual, and then continued home trusting that no immediate hazard existed. I subsequently set up an appointment with the dealership for a checkup. A week later, the dealership downloaded a new software package from GMC. The Brake Assist light did not appear when the engine started, so I left for home (50-minute drive at moderate speeds). Enroute to my home, I stopped at a store and turned the engine off. Started home a few minutes later. While accelerating past 45 mph, the brake system independently engaged, which threw me against the steering wheel and into the windshield. As the SUV decelerated through 20 mph, the brakes automatically released. I was not hurt, nor did I lose angular control of the vehicle. I completed my drive home and parked the Yukon normally. Did not drive it again until returning to the dealership a few days later. This second visit did not bear fruit. After significant explorative work, the lead mechanic drove the vehicle several miles under a multitude of conditions, but could not duplicate the problem or get the light on the DIC to extinguish. At my request, the dealership returned possession to me with the light still illuminated. I have driven the vehicle several miles since then with the "Service Brake Assist" light still illuminated. I suspect this is a GMC software problem.
This new 2021 GMC Yukon Denali we purchased on June 2, 2021 has a very sophisticated controls system that includes a feature, entitled "Brake Assist," that is designed to detect "rapid brake pedal applications due to emergency braking situations and provides additional braking to activate the Antilock Brake System (ABS) if the brake pedal is not pushed hard enough to activate ABS normally." "Brake Assist disengages when the brake pedal is released." After I left the dealership (June 2nd), I noticed that the "Service Brake Assist" light had illuminated on the Driver Information Center (DIC). I pulled off the road to check the Owner's Manual, and then continued home trusting that no immediate hazard existed. I subsequently set up an appointment with the dealership for a checkup. A week later, the dealership downloaded a new software package from GMC. The Brake Assist light did not appear when the engine started, so I left for home (50-minute drive at moderate speeds). Enroute to my home, I stopped at a store and turned the engine off. Started home a few minutes later. While accelerating past 45 mph, the brake system independently engaged, which threw me against the steering wheel and into the windshield. As the SUV decelerated through 20 mph, the brakes automatically released. I was not hurt, nor did I lose angular control of the vehicle. I completed my drive home and parked the Yukon normally. Did not drive it again until returning to the dealership a few days later. This second visit did not bear fruit. After significant explorative work, the lead mechanic drove the vehicle several miles under a multitude of conditions, but could not duplicate the problem or get the light on the DIC to extinguish. At my request, the dealership returned possession to me with the light still illuminated. I have driven the vehicle several miles since then with the "Service Brake Assist" light still illuminated. I suspect this is a GMC software problem.
This new 2021 GMC Yukon Denali we purchased on June 2, 2021 has a very sophisticated controls system that includes a feature, entitled "Brake Assist," that is designed to detect "rapid brake pedal applications due to emergency braking situations and provides additional braking to activate the Antilock Brake System (ABS) if the brake pedal is not pushed hard enough to activate ABS normally." "Brake Assist disengages when the brake pedal is released." After I left the dealership (June 2nd), I noticed that the "Service Brake Assist" light had illuminated on the Driver Information Center (DIC). I pulled off the road to check the Owner's Manual, and then continued home trusting that no immediate hazard existed. I subsequently set up an appointment with the dealership for a checkup. A week later, the dealership downloaded a new software package from GMC. The Brake Assist light did not appear when the engine started, so I left for home (50-minute drive at moderate speeds). Enroute to my home, I stopped at a store and turned the engine off. Started home a few minutes later. While accelerating past 45 mph, the brake system independently engaged, which threw me against the steering wheel and into the windshield. As the SUV decelerated through 20 mph, the brakes automatically released. I was not hurt, nor did I lose angular control of the vehicle. I completed my drive home and parked the Yukon normally. Did not drive it again until returning to the dealership a few days later. This second visit did not bear fruit. After significant explorative work, the lead mechanic drove the vehicle several miles under a multitude of conditions, but could not duplicate the problem or get the light on the DIC to extinguish. At my request, the dealership returned possession to me with the light still illuminated. I have driven the vehicle several miles since then with the "Service Brake Assist" light still illuminated. I suspect this is a GMC software problem.
This new 2021 GMC Yukon Denali we purchased on June 2, 2021 has a very sophisticated controls system that includes a feature, entitled "Brake Assist," that is designed to detect "rapid brake pedal applications due to emergency braking situations and provides additional braking to activate the Antilock Brake System (ABS) if the brake pedal is not pushed hard enough to activate ABS normally." "Brake Assist disengages when the brake pedal is released." After I left the dealership (June 2nd), I noticed that the "Service Brake Assist" light had illuminated on the Driver Information Center (DIC). I pulled off the road to check the Owner's Manual, and then continued home trusting that no immediate hazard existed. I subsequently set up an appointment with the dealership for a checkup. A week later, the dealership downloaded a new software package from GMC. The Brake Assist light did not appear when the engine started, so I left for home (50-minute drive at moderate speeds). Enroute to my home, I stopped at a store and turned the engine off. Started home a few minutes later. While accelerating past 45 mph, the brake system independently engaged, which threw me against the steering wheel and into the windshield. As the SUV decelerated through 20 mph, the brakes automatically released. I was not hurt, nor did I lose angular control of the vehicle. I completed my drive home and parked the Yukon normally. Did not drive it again until returning to the dealership a few days later. This second visit did not bear fruit. After significant explorative work, the lead mechanic drove the vehicle several miles under a multitude of conditions, but could not duplicate the problem or get the light on the DIC to extinguish. At my request, the dealership returned possession to me with the light still illuminated. I have driven the vehicle several miles since then with the "Service Brake Assist" light still illuminated. I suspect this is a GMC software problem.
DRIVING APPROX. 62 MPH ON A HIGHWAY, WENT TO SLOW DOWN AND UNABLE TO BRAKE, UPON PUSHING DOWN ON THE BREAK THERE WAS RESISTANCE, AFTER PUMPING THE BREAKS MULTIPLE TIMES I WAS EVENTUALLY ABLE TO SLOW DOWN WITH A LOT OF FORCE. MESSAGES ON DASHBOARD READ "BRAKE SYSTEM FAILURE" "62 MAX SPEED ESC, SERVICE ESC, SERVICE TRAILER BREAK SYSTEM, AND FORWARD COLLISION SYSTEM UNAVAILABLE." ABS, ESC AND CHECK ENGINE LIGHT ALL ILLUMINATED ON DASH SCREEN.
DRIVING APPROX. 62 MPH ON A HIGHWAY, WENT TO SLOW DOWN AND UNABLE TO BRAKE, UPON PUSHING DOWN ON THE BREAK THERE WAS RESISTANCE, AFTER PUMPING THE BREAKS MULTIPLE TIMES I WAS EVENTUALLY ABLE TO SLOW DOWN WITH A LOT OF FORCE. MESSAGES ON DASHBOARD READ "BRAKE SYSTEM FAILURE" "62 MAX SPEED ESC, SERVICE ESC, SERVICE TRAILER BREAK SYSTEM, AND FORWARD COLLISION SYSTEM UNAVAILABLE." ABS, ESC AND CHECK ENGINE LIGHT ALL ILLUMINATED ON DASH SCREEN.