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General Motors just announced it will debut the second-generation Duramax Diesel engine in 2023 for some Chevy Silverado 1500 and GMC Sierra 1500 pickups. This is the first change for the LM2 (now named LZ0) six-cylinder turbodiesel engine since its 2019 introduction. GM says it has redesigned 25% of the Duramax, increasing power to 305 hp and torque to 495 lb-ft. So, will these changes improve performance and reliability?

Why is the Duramax diesel extended inspection time a big deal?

Two 2023 GMC Sierra 1500 trucks parked next to each other.
2023 GMC Sierra 1500 models | GMC

GM is confident enough about the new LZ0 Duramax diesel engine’s reliability that it has extended its recommended inspection to 200,000 miles. The significance is huge. That’s because, in the previous generation, you had to drop the transmission to replace the variable valve oil pump belt at 100,000 miles. It’s located at the back of the crankcase. Yeah, not the best design.

Another improvement fixes one of the Duramax diesel’s biggest problems: starting issues. Owners have complained the engine takes a long cranking time to fire up. That or it doesn’t start at all. The solution has been to give it a few seconds to rest and then try again. Eventually, it would fire up. 

Did GM fix the Duramax diesel engine’s starting issues?

GM engineers spent considerable time addressing the Duramax diesel engine’s starting problems. Supplier-damaged camshaft position sensor exciter wheels, or trigger wheels, were the culprit. In 2021, a technical service bulletin (PIP5806) announced the problem. The trigger wheel would become bent, requiring replacement.

But they also discovered some trigger wheel teeth were getting bent, too. So, the solution involved a different crank design to improve tooth engagement on LM2 engines. The new LZ0 Duramax also received this fix. Thus, the mystery of the starter/cranking issues was finally solved.

Another durability improvement is with pistons. The previous-generation LM2 engines used aluminum pistons. The new LZ0 uses smaller steel pistons. Why smaller? GM diesel engineer John Barta told Pickup Truck Plus SUV Talk the change adds a longer stroke while maintaining the 3.0-liter displacement. 

How did GM improve the engine’s power?

A 2023 Chevrolet Chevy Suburban High Country full-size SUV model with available Duramax Turbo-Diesel engine
2023 Chevy Suburban High Country | Chevrolet

Another difference in the LZ0 Duramax diesel engine is that it uses new injectors to help increase turbocharger tuning. That boosts its power. And a significant change comes with an entirely redesigned cylinder head. Beyond those modifications is a redesigned cooling system. 

For 2023 GM trucks, the new Duramax diesel engine will be available in Custom Trail Boss, LT, RST, LT Trail Boss, LTZ, and High Country trims. It won’t be available in the ZR2 or ZR2 Bison. Also, Chevy Tahoe, Chevy Suburban, GMC Sierra, and GMC Yukon SUVs will get the new Duramax. But that won’t happen until after 2023.