This Problem Across All Years
I own a 2021 Chevrolet Silverado 2500HD Duramax diesel with approximately 100,300 miles. The truck began displaying a “Service Emissions System” warning and a countdown message that in a certain number of miles the vehicle will be limited in speed (for example to 65 mph). GM’s own Duramax diesel owner’s supplement explains that when a “Service Emission System” message appears it is accompanied by a distance-until-speed-limit countdown and that the truck will progressively limit speed first to about 65 mph and then to about 55 mph if the condition is not corrected, telling the owner to see the dealer. This creates a safety risk because the derate can occur while driving on highways or rural roads, where an unexpected limit on maximum speed can interfere with merging, passing, and keeping up with traffic. This is our only vehicle, and we must use it for important medical appointments, including cardiology and surgery-related visits. The condition started only about 300 miles beyond GM’s 5-year / 100,000-mile powertrain warranty. I opened a case with Chevrolet / GM Corporate (Service Request No. XXX) and took the truck to Sons Chevrolet in Columbus, Georgia on November 17, 2025 for this issue and a rear wheel lockup recall. The dealer kept the truck from about 9:00 a.m. to 3:00 p.m. and indicated they might need to keep it for at least two more days, but I was not given a clear written explanation of the diagnostic trouble codes or a firm repair plan. Because GM’s own manuals describe this “Service Emission System” message together with speed-limit countdowns, and because the vehicle can actively limit speed on the road if the fault is not resolved, I am concerned this represents a broader emissions/derate defect on late-model Silverado HD Duramax trucks. I request that NHTSA review similar complaints and consider whether further investigation or a safety recall is warranted. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
I own a 2021 Chevrolet Silverado 2500HD Duramax diesel with approximately 100,300 miles. The truck began displaying a “Service Emissions System” warning and a countdown message that in a certain number of miles the vehicle will be limited in speed (for example to 65 mph). GM’s own Duramax diesel owner’s supplement explains that when a “Service Emission System” message appears it is accompanied by a distance-until-speed-limit countdown and that the truck will progressively limit speed first to about 65 mph and then to about 55 mph if the condition is not corrected, telling the owner to see the dealer. This creates a safety risk because the derate can occur while driving on highways or rural roads, where an unexpected limit on maximum speed can interfere with merging, passing, and keeping up with traffic. This is our only vehicle, and we must use it for important medical appointments, including cardiology and surgery-related visits. The condition started only about 300 miles beyond GM’s 5-year / 100,000-mile powertrain warranty. I opened a case with Chevrolet / GM Corporate (Service Request No. XXX) and took the truck to Sons Chevrolet in Columbus, Georgia on November 17, 2025 for this issue and a rear wheel lockup recall. The dealer kept the truck from about 9:00 a.m. to 3:00 p.m. and indicated they might need to keep it for at least two more days, but I was not given a clear written explanation of the diagnostic trouble codes or a firm repair plan. Because GM’s own manuals describe this “Service Emission System” message together with speed-limit countdowns, and because the vehicle can actively limit speed on the road if the fault is not resolved, I am concerned this represents a broader emissions/derate defect on late-model Silverado HD Duramax trucks. I request that NHTSA review similar complaints and consider whether further investigation or a safety recall is warranted. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
DEF system failure causing truck to enter limp mode being reduced to 65 MPH, then 55 MPH, and then restricted to 5 MPH. Error in def system led to DEF heater to go bad causing the incident to occur.
DEF system failure causing truck to enter limp mode being reduced to 65 MPH, then 55 MPH, and then restricted to 5 MPH. Error in def system led to DEF heater to go bad causing the incident to occur.
The DEF heater short circuit and derates the truck. If the government says we have to have this they should cover the cost to fix it.
The DEF heater short circuit and derates the truck. If the government says we have to have this they should cover the cost to fix it.
JULY 2022 DPF filter was throwing check engine light. Took to dealer to get diagnosed, part was ordered and the DPF was replaced August 19th 2022. Started to get headaches in vehicle while driving it. OCT 9th ended up in hospital after driving vehicle and was diagnosed with CARBON MONOXIDE POISONING. Experienced symptoms of losing consciousness, worst headache I've ever had, nausea for 5 hours, loss of feeling in body and seizing of body. Took truck to dealer to get inspected twice and nothing was found to be wrong with it. NOV 10th Took truck on another road trip and was having similar symptoms as before however had more chest pain this time so went back to hospital. Took truck back to dealer to have inspected again and was told that it was fine. Nov 18th took truck on another road trip and within 20 mins of driving had another horrible headache. Pulled over and needed to get air and ended up driving truck 4 hours home with windows and sunroof open to avoid getting carbon monoxide poisoning again. I have been ill since August and that is due to diesel and carbon monoxide poisoning every single time I drive the vehicle which is daily. The truck has been now at the dealership for 70 days without any update or improvement in the case.
JULY 2022 DPF filter was throwing check engine light. Took to dealer to get diagnosed, part was ordered and the DPF was replaced August 19th 2022. Started to get headaches in vehicle while driving it. OCT 9th ended up in hospital after driving vehicle and was diagnosed with CARBON MONOXIDE POISONING. Experienced symptoms of losing consciousness, worst headache I've ever had, nausea for 5 hours, loss of feeling in body and seizing of body. Took truck to dealer to get inspected twice and nothing was found to be wrong with it. NOV 10th Took truck on another road trip and was having similar symptoms as before however had more chest pain this time so went back to hospital. Took truck back to dealer to have inspected again and was told that it was fine. Nov 18th took truck on another road trip and within 20 mins of driving had another horrible headache. Pulled over and needed to get air and ended up driving truck 4 hours home with windows and sunroof open to avoid getting carbon monoxide poisoning again. I have been ill since August and that is due to diesel and carbon monoxide poisoning every single time I drive the vehicle which is daily. The truck has been now at the dealership for 70 days without any update or improvement in the case.
Starting smelling gas inside of the cab, at first thought it was non-issue, but the smell persisted. Several days passed, and when I went to warm up my truck in the morning smelled a strong gas odor, and when I looked under the engine - there was a pool of gas, and gas was leaking. Took it in to the dealership (thinking it was a simple loose filter line) but they now say that it is more than that. Not sure if this has been a re-occurring issue with these new trucks, but it could have been a very dangerous situation.
Starting smelling gas inside of the cab, at first thought it was non-issue, but the smell persisted. Several days passed, and when I went to warm up my truck in the morning smelled a strong gas odor, and when I looked under the engine - there was a pool of gas, and gas was leaking. Took it in to the dealership (thinking it was a simple loose filter line) but they now say that it is more than that. Not sure if this has been a re-occurring issue with these new trucks, but it could have been a very dangerous situation.