21:42 11-11-2025

GM investigates Duramax LZ0 misfires at 55–70 mph in 2024–2026 models

General Motors has launched an official investigation after reports of occasional misfires in the 3.0-liter inline-six Duramax LZ0 diesel. The issue has been noted on several models—from Chevrolet Silverado and GMC Sierra pickups to the Tahoe, Suburban, and Yukon SUVs—built for the 2024–2026 model years.

Preliminary information in service bulletin PIP6091, published in October 2025, indicates the fault may stem from condensate entering the engine. That can trigger brief combustion interruptions, felt as vibration or a hesitation under acceleration at 55–70 mph. In practice, a moisture-related stumble at those speeds is the kind of quirk drivers notice immediately, even if it lasts only a moment.

A complicating factor is that the diagnostics do not always flag an error—no trouble code may appear. When a code is recorded, the misfires most often involve the third and fourth cylinders. That mismatch between feel and diagnostics tends to frustrate owners.

GM engineers have confirmed they are actively investigating and are preparing a comprehensive technical update to the repair instructions. The early working theory points to characteristics of the intake design and the way moisture behaves during extended driving. That diagnosis would align with the noted speed window and the transient nature of the symptoms.

The LZ0 is an evolution of the earlier LM2 and delivers 305 hp and 671 Nm of torque, up from 277 hp and 624 Nm. It pairs with a 10-speed automatic and is positioned as a reliable, fuel-efficient next-generation diesel; even so, a clear, timely fix will be key to maintaining that promise.