General Motors’ troublesome 6.2-liter L87 V8 is back under an even brighter federal spotlight. The National Highway Traffic Safety Administration has expanded its investigation into the engine after receiving hundreds of complaints alleging failures even after vehicles received GM’s recall remedy. The newly opened Engineering Analysis covers 997,743 vehicles from the 2021 through 2026 model years, including the Cadillac Escalade, Chevrolet Silverado 1500, Suburban and Tahoe, along with the GMC Sierra 1500, Yukon and Yukon XL.

This is a significant escalation for a problem GM has been dealing with for years. The automaker recalled nearly 600,000 L87-powered trucks and SUVs last year over the possibility of serious internal engine damage and sudden loss of power. Depending on inspection results, owners were given one of two remedies. Some vehicles received higher-viscosity engine oil, while others required a complete engine replacement. NHTSA is now questioning how effective those fixes have been after complaints continued rolling in.

According to the agency, 499 complaints involve vehicles that allegedly suffered engine failures after the recall work was completed. Of those, 473 had received the oil-viscosity remedy, while 26 had been fitted with replacement engines. That alone would be enough to keep regulators interested, but there is another wrinkle. NHTSA has also received 191 reports involving L87 engines produced after May 31, 2024, which was the end of the production period covered by the original recall. GM, meanwhile, reported receiving 6,953 complaints involving post-remedy engine failures.

The L87 investigation has become particularly frustrating because this is far from the first time regulators have examined the 6.2-liter V8. Earlier inquiries stretched back several years before the major recall finally arrived. GM previously traced the issue to supplier manufacturing and quality problems that could result in crankshafts being produced outside specification and damage to connecting-rod bearings. When that type of internal failure happens, an engine can seize with little warning, potentially leaving a heavy truck or SUV without propulsion in traffic. That is why this has always been more serious than a typical reliability complaint.

For GM, the expanded probe raises an uncomfortable question: Did the original recall actually solve the L87 problem, or merely reduce it? An Engineering Analysis does not automatically mean another recall is coming, but it gives NHTSA a deeper look at the failure pattern, GM’s repair strategy, and engines built outside the original recall window. With nearly 1 million vehicles now included in the investigation and reports continuing after both oil changes and complete engine replacements, this 6.2-liter V8 headache appears to be a long way from finished.