General Motors has issued a new service bulletin for 2026 Chevrolet Silverado 2500HD and 3500HD and 2026 GMC Sierra 2500HD and 3500HD trucks equipped with the 6.6L L5P Duramax turbo-diesel V8. Bulletin PIP6131, dated August 2026, addresses an abnormal upper engine noise, and in confirmed cases the prescribed repair is significant: replacement of the engine and turbocharger.
PIP6131 is a Preliminary Information bulletin, the document GM sends to dealership technicians when a condition has been identified but a final, formal repair procedure is still being developed. It applies to all VINs and all transmissions, across North America.
What Owners May Notice
According to the bulletin, some customers may comment on an abnormal noise from the engine. GM describes the sound three ways: a tick, a screech, or a grinding noise. The noise may also be accompanied by an engine misfire, shaking, or vibration.
GM attributes the condition to a lack of lubrication, specifically insufficient oil flow, to the rocker shafts or rocker arm components in the upper end of the engine. The rocker arms sit at the top of the valvetrain and depend on steady oil delivery. When that flow is interrupted, metal-on-metal contact produces exactly the kind of noise the bulletin describes.
Bulletin PIP6131 at a Glance
The Prescribed Repair
The diagnostic procedure GM lays out for technicians is direct. Remove the rocker arm cover from the bank of the engine that sounds the loudest, then inspect for signs of lack of lubrication.
If the technician confirms the rocker shafts or rocker arm components have been starved of oil, the correction is to replace the engine and the turbocharger. GM is not prescribing a rocker arm or rocker shaft repair here. Once lubrication has been lost at the top of the engine, debris and wear can travel well beyond the valvetrain, which explains why the turbocharger, fed by the same oil system, is included in the replacement.
What This Means for Owners
A few points worth keeping in perspective. This is a service bulletin, not a recall. It exists to help dealership technicians diagnose a condition that some trucks may exhibit, and it does not mean every 2026 HD with the L5P is affected.
That said, if your 2026 Silverado HD or Sierra HD develops a tick, screech, or grinding noise from the engine, especially with a misfire or new vibration, get it to your dealer promptly and reference PIP6131. Continuing to run an engine with oil-starved rocker components risks additional damage. These trucks are covered by GM’s Duramax powertrain warranty, and the inspection outlined in the bulletin is the fastest path to a documented diagnosis.
Because this is a Version 1 Preliminary Information bulletin, expect GM to update it as the investigation matures. Revised versions often narrow the affected build range or add part information, and we will report on any updates. You can keep up with this bulletin and others in our TSB archive.
Join the Discussion
Is your 2026 Duramax HD making an unusual noise, or has your dealer already performed this inspection? Share your experience with thousands of fellow owners in our 2020-2026 Silverado HD & Sierra HD forum.
Zane Merva is the Executive Editor of GM-Trucks.com and the President of the New England Motor Press Association (NEMPA). A veteran automotive journalist with over 26 years of experience, Zane is a designated ‘Car Talk’ Expert and has been a contributor to The Boston Globe. He possesses a unique evaluative perspective, having road-tested more than 2,000 vehicles across every major manufacturer. While he is a recognized authority on General Motors truck platforms—including the Silverado, Sierra, and Colorado—his expertise is grounded in decades of deep competitive analysis that few in the industry can match. His commentary has been featured by major OEMs and media outlets, including Hyundai and PR Newswire