GMC Sierra 1500 won't shift problems

Filed Nov 3, 2026 · Brakes, Electrical · OK

While the truck was under warranty it would go into limp mode. A dealer said they replaced the valve body but it did not look like anything had been done to it. It didn’t go into limp mode and seemed fine for a couple of months then it went into limp mode again and we took it back to the dealership. The hooked a scanner up and cleared the codes and it worked fine for a couple of more months. (This cycle happened repeatedly until it was out of the warranty.) We finally got our own scanner and cleared the codes like they did at the dealer and it would work fine for a while. Then one day driving at 60-65 mph it locked the rear wheels and we slid off into the ditch. It happened 4 more times before we got it home. (We were driving about 15 mph). We called the dealership and they said they couldn’t do anything since it was out of warranty and it could need a new transmission. It was never right from the time we bought it. The locking brakes could be fatal if it had happened on a busy highway. The first problem we had with it was the front grill flew off. We called the same dealer and they told us we pushed too hard on it closing the hood so they weren’t responsible. My husband fixed it and it never came off again but we saw later that it had been recalled for the same problem.

Filed Oct 30, 2026 · Engine, Steering · 34,000 miles · AK

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving 45 MPH, there was an abnormal knocking sound coming from the vehicle. The vehicle started hesitating, and there was a loss of power that became worse over time. Additionally, the “Service Engine” and “Power Train” warning lights were illuminated. The messages “Loss of Steering Assist - Be Alert” and “Service Parking Brake” were displayed. The following day, the vehicle was driven in LIMP Mode to the dealer and was diagnosed with engine failure. The contact stated that there was an ongoing the federal safety agency investigation associated with the 6.2L engines. The failure mileage was approximately 34,000.

Filed Oct 15, 2026 · Engine · 110,900 miles · KY

The contact owns a 2021 GMC Sierra. The contact stated that while driving at 60 MPH, a reduced power mode warning message unexpectedly illuminated, and the vehicle unexpectedly entered limp mode. The contact stated that the temperature gauge indicated a high temperature and the vehicle was overheating during the failure. The vehicle was taken to the dealer, where it was diagnosed that the control valve had failed and needed to be replaced. The vehicle was not repaired. The dealer informed the contact that this was a known failure and escalated the issue to the manufacturer for further assistance. The contact stated that the failure was associated with Technical Service Bulletin (TSB) N252508340 and believed the repair should have been covered under warranty. The manufacturer was made aware of the failure via telephone and website. The contact was also referred to the federal safety agency for further assistance. The approximate failure mileage was 110,900.

Filed Oct 15, 2026 · Brakes, Engine · TX

On 10/15/2026 I was making a slow right-hand turn up a slight incline into a parking lot when the vehicle braked very hard and the transmission made a grinding noise. I looked at the dashboard, and it was showing that the truck shifted into park while I was driving. The electronic brake engaged as well. I tried putting the truck back into drive, but it would not go into drive. On the dash there was a Service Transmission warning. The push to start engine button still had the green LED on as if the vehicle was running. I pushed the start engine button and the engine started (I didn't realize until now that the engine had shut off). At this point the truck would shift into drive. Another point of note is that I had turned off the Auto Stop feature. I do this every time I start my trip. The truck will be looked at on 10/16/2026 by the dealership. I did report the problem to the service department of the dealership. This incident was the first time it ever happened and there was no warning.

Filed Oct 13, 2026 · Engine · 107,000 miles · CT

The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle suddenly entered Limp mode without warning. The vehicle was taken to the dealer, where the computer was reflashed and the vehicle temporarily returned to normal operation; however, the failure recurred and the vehicle was returned to the dealer. The contact noticed a burnt odor coming from the engine compartment, along with engine bay cooling fans running at an unusual rate. Upon further inspection, the dealer diagnosed the failure as a defective coolant valve. The contact associated the failure with GM Special Coverage TSB N252508341; however, the VIN was not included in the coverage program. The manufacturer was notified of the failure. The failure mileage was 107,000.

Filed Oct 11, 2026 · Engine · ND

1) Driving on highway and lost acceleration power would only go 50 mph/went into limp mode. Dealership stated VIN number had not been released into national safety recall. Replaced crank shaft valve and was told once VIN was released I would be reimbursed, to date still in dispute. 2) low oil light came on, upon checking oil was extremely low and oil had just been changed during #1’s repair. Had towed to dealership. Engine was replaced under recall. Was charged for water pump which is in dispute. 3) shortly after and well before oil change would be due, low oil light came on again. Towed back to dealership dip stick bone dry. I asked the store vehicle inside. Called for diagnosis at 5pm stated no codes no leaks found needed to investigate further. 4) 9am following day received a vm the truck had been repossessed by GM (note there is only 10K remaining on a special order 72K truck) dealership has not responded to requests to determine if the issue was fixed or request for service ticket to know what had been done. GM Financial claimed dealership told them it “was just a part under warranty” well the warranty came from the replacement engine that was under the recall…upon talking to reinstatement dept I was informed the vehicle was not fixed. I will be redeeming the vehicle but I do not think it is right to repo during a safety recall and then auction off not fixed as that is a safety issue! Once redeemed, it is also a safety issue to get from auction lot to be repaired.

Filed Oct 6, 2026 · Engine, Fuel system · LA

While driving on a public road, the 6.2L L87 V8 stalled without warning. There was heavy smoke and an oil trail of about 300 yards behind the truck. The engine would not restart, and the transmission would not shift into neutral. The truck was moved a short distance off the road and towed the next day to the selling GMC dealer. Odometer was 4,663 miles. Oil life remaining was 38 percent. The truck was stock, with no modifications, and was operated on premium fuel. No warning lamp was noticed before the stall. The failed engine is at the dealer and currently under inspection. The dealer inspection is not finished, and no written cause has been provided. This is a sudden loss of propulsion. Please associate this report with Engineering Analysis EA26005 concerning connecting-rod and crankshaft failures in the GM 6.2L L87 engine.

Filed Oct 2, 2026 · Brakes, Driver assistance · TX

Electronic braking system failure. Vehicle was put in limp mode with a top speed of 62 MPH. Vehicle had very little or no braking . Vehicle has less than 13,000 miles . I am the original owner.

Filed Sep 30, 2026 · Engine · IA

There is an known issue with the coolant control valve that causes the truck to enter "limp mode" that dangerously reduces the engine power. The part is not recalled but there is a special extended warranty, N252508341, up to 15yrs or 150,000 miles for 2021-2022 GMC 1500 trucks but my VIN is excluded from this for some reason. I would like this investigated.

Filed Sep 29, 2026 · Transmission · 74,200 miles · IN

The contact owns a 2024 GMC Sierra 1500. The contact stated that while driving 55 MPH, the message "Reduced Acceleration" was displayed and the vehicle decelerated quickly, and the contact was forced to pull over to the side of the road. The vehicle was taken to the dealer on several occasions to be diagnosed. During the first visit, the dealer stated that a transmission error code was retrieved and was cleared before the vehicle was returned. During the second visit, the dealer stated that the engine was consuming an excessive amount of engine oil and recommended that the engine be replaced. The contact stated that the message "Reduce Acceleration - Drive with Care" was displayed, and the vehicle went into LIMP Mode. Occasionally, after shifting to drive(D), the engine revved but the vehicle failed to respond, and the vehicle was taken back to the dealer. The manufacturer was notified of the failure. The failure mileage was 74,200.