This Problem Across All Years
This is the second time in 2 days!! While driving ~35MPH the truck experienced a harsh transmission shift followed by a sudden loss of acceleration and entered shutdown mode to protect the engine. The steering became stiff, all dashboard warning lights illuminated, and a message appeared on the driver display indicating a transmission issue and advising to drive with caution. This created an extremely hazardous condition for me while driving on s busy stretch of road. I pulled onto the side of the road, came to a complete stop, shifted into park, and turned off the engine. Upon restarting the vehicle, the Check Engine Light remained on, and the transmission continued to shift abnormally at low speeds, including some noticeable shuddering. My GMC application recorded the issue and reminded me to schedule service.
While in the parking lot of a local grocery store, I shifted the vehicle into reverse, at which point all dashboard warning lights immediately illuminated and the braking response became significantly weakened and nearly unresponsive. I placed the vehicle back into park, paused, and then attempted to shift into reverse again, but the dashboard alerts and brake issue persisted. This created a very unsafe driving situation because the brake system was very unresponsive. Despite the unsafe condition, I cautiously drove to my home 2miles away at a speed of under 20 MPH, requiring excessive brake pressure to bring the vehicle to a stop. I parked the vehicle in my driveway and left it there overnight. The next morning, I tested the brakes, and they seemed to return to normal so I drove 5 miles to my local GMC service center. Service Tech confirmed Check Engine Light On and reported code P0700 and P00FF in the report.
This is the second time in 2 days!! While driving ~35MPH the truck experienced a harsh transmission shift followed by a sudden loss of acceleration and entered shutdown mode to protect the engine. The steering became stiff, all dashboard warning lights illuminated, and a message appeared on the driver display indicating a transmission issue and advising to drive with caution. This created an extremely hazardous condition for me while driving on s busy stretch of road. I pulled onto the side of the road, came to a complete stop, shifted into park, and turned off the engine. Upon restarting the vehicle, the Check Engine Light remained on, and the transmission continued to shift abnormally at low speeds, including some noticeable shuddering. My GMC application recorded the issue and reminded me to schedule service.
While in the parking lot of a local grocery store, I shifted the vehicle into reverse, at which point all dashboard warning lights immediately illuminated and the braking response became significantly weakened and nearly unresponsive. I placed the vehicle back into park, paused, and then attempted to shift into reverse again, but the dashboard alerts and brake issue persisted. This created a very unsafe driving situation because the brake system was very unresponsive. Despite the unsafe condition, I cautiously drove to my home 2miles away at a speed of under 20 MPH, requiring excessive brake pressure to bring the vehicle to a stop. I parked the vehicle in my driveway and left it there overnight. The next morning, I tested the brakes, and they seemed to return to normal so I drove 5 miles to my local GMC service center. Service Tech confirmed Check Engine Light On and reported code P0700 and P00FF in the report.
While driving on the highway at 70 MPH, the truck experienced a harsh transmission shift followed by a sudden loss of acceleration and entered shutdown mode to protect the engine. The steering became stiff, all dashboard warning lights illuminated, and a message appeared on the driver display indicating a transmission issue and advising to drive with caution. The RPMs surged and the truck struggled to maintain a speed of 45 MPH while the remaining at 4000 RPM. This created an extremely hazardous situation for both me and my passenger. I safely pulled into the breakdown lane, came to a complete stop, shifted into park, and turned off the engine. Upon restarting the vehicle, the Check Engine Light remained on, and the transmission continued to shift abnormally at low speeds, including noticeable shuddering.
While driving on the highway at 70 MPH, the truck experienced a harsh transmission shift followed by a sudden loss of acceleration and entered shutdown mode to protect the engine. The steering became stiff, all dashboard warning lights illuminated, and a message appeared on the driver display indicating a transmission issue and advising to drive with caution. The RPMs surged and the truck struggled to maintain a speed of 45 MPH while the remaining at 4000 RPM. This created an extremely hazardous situation for both me and my passenger. I safely pulled into the breakdown lane, came to a complete stop, shifted into park, and turned off the engine. Upon restarting the vehicle, the Check Engine Light remained on, and the transmission continued to shift abnormally at low speeds, including noticeable shuddering.
The vehicle was purchased for the express purpose of towing a 6,600 lbs Travel Trailer. This truck is equipt with the 3 liter Diesel engine. While towing the truck computer counts down milage available based on Def level. The count down is not mile for mile it is an exponential count down. This factor triggers a series of warnings concerning vehicle operation and impending speed restrictions. 1000 mile DEF range warning is first up. Followed shortly there after with a 300 mile DEF range warning (700 miles had never been reached to trigger the warning). The next warning is "DEF Low (red warning) speed restricted soon". Shortly there after a 500 mile count down starts for the first impending speed reduction to 65 MPH max. This is followed by other speed restrictions that will put the vehicle eventually into a 5 MPH speed restricted mode. When adding DEF to the tank the level has never been below 60% full. Its not empty as the gauge and computer indicate. With each filling of the DEF tank the range you can drive is less and less until the truck is driven without the trailer hooked up. GM has a service bulletin for this situation that has been in place since September 23, 2024 and no permanent repair of solution has been prescribed. During the 500 mile count down to the first speed restriction the instrument cluster is locked out to only display "DEF Empty" and alternately the DEF range counting down. No other safety features are visible such as engine temp or transmission temp important to know while towing. I Purchased this vehicle March 17, 2025 stating my intentions to tow a travel trailer. The dealership no GMC ever made me aware of the Service bulletin of the DEF restrictions. Had they done so I would have purchased a different vehicle with out the associated travel issues. Please reference GM Service Bulletin #24-NA-196 Document ID 6736285. This document was given to me after my 4 visit to a GMC dealership to have the issue addressed.
The vehicle was purchased for the express purpose of towing a 6,600 lbs Travel Trailer. This truck is equipt with the 3 liter Diesel engine. While towing the truck computer counts down milage available based on Def level. The count down is not mile for mile it is an exponential count down. This factor triggers a series of warnings concerning vehicle operation and impending speed restrictions. 1000 mile DEF range warning is first up. Followed shortly there after with a 300 mile DEF range warning (700 miles had never been reached to trigger the warning). The next warning is "DEF Low (red warning) speed restricted soon". Shortly there after a 500 mile count down starts for the first impending speed reduction to 65 MPH max. This is followed by other speed restrictions that will put the vehicle eventually into a 5 MPH speed restricted mode. When adding DEF to the tank the level has never been below 60% full. Its not empty as the gauge and computer indicate. With each filling of the DEF tank the range you can drive is less and less until the truck is driven without the trailer hooked up. GM has a service bulletin for this situation that has been in place since September 23, 2024 and no permanent repair of solution has been prescribed. During the 500 mile count down to the first speed restriction the instrument cluster is locked out to only display "DEF Empty" and alternately the DEF range counting down. No other safety features are visible such as engine temp or transmission temp important to know while towing. I Purchased this vehicle March 17, 2025 stating my intentions to tow a travel trailer. The dealership no GMC ever made me aware of the Service bulletin of the DEF restrictions. Had they done so I would have purchased a different vehicle with out the associated travel issues. Please reference GM Service Bulletin #24-NA-196 Document ID 6736285. This document was given to me after my 4 visit to a GMC dealership to have the issue addressed.
I WAS DRIVING ON A PA ROAD AT ABOUT 30 MPH. MY CAR STOPPED IMMEDIATELY AND I HEARD THE MOTOR REV. THE CAR THEN SLAMMED INTO A STOP.
I WAS DRIVING ON A PA ROAD AT ABOUT 30 MPH. MY CAR STOPPED IMMEDIATELY AND I HEARD THE MOTOR REV. THE CAR THEN SLAMMED INTO A STOP.