May 9, 2026Electrical systemEngineFuel system
GM Duramax L5P diesel engine electrical connector for #4 fuel injector. This failure caused the Diesel exhaust brake, which controls downhill speed, to disengage, extreme shaking of the vehicle, emissions system warning and speed limiting. This occurred while descending a steep grade while towing a 34 feet long, 10,000 pound trailer. This is a known issue with this diesel engine and documented in GM Technical Service Bulletin 23-NA-027. Inspection and repair at a GM dealership confirmed a known issue with the #4 injector pigtail connector caused by improper wire routing and interference wit the Sound Shield and Valve Cover Heat Shield This was a sudden failure of the #4 pigtail connector with no advance warning. In addition to violent shaking of the vehicle, multiple warnings on the DIC indicating that the Diesel Brake was disengaged, the emission system had an issue, and speed would be limited.
NHTSA ODI 11736800
Nov 7, 2023EngineFuel system
Metal in the fuel filter and throughout the fuel system, 38 codes on the computer just in 2 weeks after a full service again at the dealer. All service has been preformed at A GMC Dealer since truck was serviced. 1. P026D - Fuel injection Quantity “A” Higher then expected 2. P06CC - cylinder 8 incorrect 3. P133F - cylinder 8 glow plug offset exceeding learning limits None stop this is happening since [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
NHTSA ODI 11553906
Nov 2, 2023EngineFuel system
Constant issues with glow plug failures, fuel rail failure, fuel pressure failure. Truck has been in the Gmc service regarding these issues constantly for the last year with a total of five repairs and replacement of glow plugs with releaning learning new plugs and now the 6th return to the shop they’re tearing down the fuel system. Malfunction and engine light consistently come on with the same occurring problems generating from the fuel system and glow plugs. Fuel mileage is absolutely terrible and lose of power hazardous to safety!!! Gmc has issued an extended warranty for 15 years and 150,000 miles, but cant and hasn’t found a repair for vehicle and just replaces the glow plugs just so they can fail again and again!!! They need to replace everything that needs to be done and if no fix they need LEMON Law The vehicle. This is ridiculous going back to the shop every two weeks I have my truck in the shop for a month to get it back, to put it back in the shop two weeks later, to have it back in the shop for a month. Since this start 17months ago I’ve only been able to put less then 7000 miles on the vehicle because GMC constantly has the truck! The is ridiculous when you’re paying $800 a month for your payment and insurance on your vehicle that you can’t drive because the manufacturer is constantly having to repair and replace the same thing over and over again
NHTSA ODI 11553304
May 30, 2023Engine
Low coolant warning light came on. I was towing a travel trailer on a very busy roadway with no place to pull off while pulling a trailer. I had to pull over to the shoulder to check the coolant level and make sure I didn’t cause major damage to my engine by letting it overheat. While waiting to let the engine cool down, I researched and found that this is a very common issue with L5P Duramax Engines in GM trucks and it is specifically related to a faulty coolant level sensor. As it turns out, my coolant level was fine and there was no issue. The danger posed by me pulling over and waiting for well over an hour on the side of the busy backroad with my son in the truck was not a necessary one. It appears that this is a well known issue that is not being addressed by GM.
NHTSA ODI 11524351
Apr 15, 2022EngineFuel system
Faulty pigtail connector for fule injectors. Cause The vehicle to shut down even while going down the highway possibly causing injury by immediate deceleration wich could cause an accident. For me on this vehicle I’ve had this happen three times and it has cost me anywhere from $800 to 1000 per injector especially if damage is done to one of the fuel injectors.
NHTSA ODI 11460968
Feb 14, 2022Engine
2018 GMC SIERRA 2500 HD. CONSUMER WRITES IN REGARDS TO ACCELERATION ISSUES. THE CONSUMER STATED THE VEHICLE DISPLAYED WARNING LIGHTS. AND BEGAN SHAKING. THE VEHICLE BECAME DIFFICULT TO ACCELERATE. THE DEALER INFORMED THE CONSUMER THAT NUMBER 4 INJECTOR WAS THE CAUSE OF THE FAILURE. THE VEHICLE WAS REPAIRED. SHORTLY AFTER, THE GLOW PLUG FAILED AND THE COMPUTER REQUIRED AN UPDATE. THE CONSUMER REQUESTED TO REIMBURSED FOR THE RENTAL VEHICLE AS WELL AS REPAIR COSTS.
NHTSA ODI 11451874
Dec 2, 2019Engine
TL* THE CONTACT OWNS A 2018 GMC SIERRA 2500. THE CONTACT RECEIVED NOTIFICATION OF NHTSA CAMPAIGN NUMBER: 19V328000 (ENGINE); HOWEVER, THE PARTS FOR THE RECALL REMEDY WERE NOT AVAILABLE. THE CONTACT STATED THAT THE MANUFACTURER EXCEEDED A REASONABLE AMOUNT OF TIME TO REPAIR THE VEHICLE. JONES BUICK GMC OF LANCASTER (1335 MANHEIM PIKE, LANCASTER, PA 17601, (717) 394-0711), TURNER BUICK GMC (612 E MAIN ST, NEW HOLLAND, PA 17557, (866) 680-8360) AND KEIM CHEVROLET INC (3265 LINCOLN HWY E, PARADISE, PA 17562, (717) 879-9614) WERE CONTACTED AND CONFIRMED THAT PARTS WERE NOT AVAILABLE AND WERE BEING SHIPPED TO THE NORTHERN STATES. THE MANUFACTURER WAS MADE AWARE OF THE FAILURE. THE CONTACT HAD NOT EXPERIENCED A FAILURE. PARTS DISTRIBUTION DISCONNECT.
NHTSA ODI 11286375
Sep 17, 2019Engine
TL* THE CONTACT OWNS A 2018 GMC SIERRA 2500. WHILE DRIVING 30-50 MPH UP A HILL, THE VEHICLE SHUDDERED. THERE WERE NO WARNING INDICATORS ILLUMINATED. THE VEHICLE WAS NOT DIAGNOSED OR REPAIRED. THE MANUFACTURER AND DEALER WERE NOT CONTACTED. THE FAILURE MILEAGE WAS 5,641. THE VIN WAS INVALID.
NHTSA ODI 11256119