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

GM is confident enough about the new LZ0 Duramax engine’s reliability that it has extended its recommended inspection to 200,000 miles. The significance of this 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 is located at the back of the crankcase. Yeah, not the best design.

And another improvement is with one of its biggest problems, starting issues. Many owners have complained that it takes a long cranking time for the Duramax to fire up. That, or it doesn’t start at all. The solution has been to give it a few seconds rest and then try again. Eventually, it would fire up. 

GM engineers spent a lot of time on the 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 that some trigger wheel teeth were getting bent, too. So the fix involved a different crank design to improve tooth engagement on LM2 engines. The new LZ0 Duramax also received this fix. So the mystery of the starter/cranking issues was finally solved.

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

Another change is utilizing new injectors to help increase turbocharger tuning. That increased its power. And a big change comes with an entirely redesigned cylinder head. Beyond those changes, there is a redesigned cooling system. 

For 2023 GM trucks, the new Duramax diesel engine will only 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, Chevrolet Tahoe/Suburban, and GMC Sierra/Yukon SUVs will also get the new Duramax. But it won’t happen until after 2023. 

You can also refer to this post for information on typical problems with the LM2 Duramax diesel engines.

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