DETROIT -- Federal safety regulators have upgraded a probe into tailgate failures on full-sized pickups built by General Motors in a possible blow to the automaker's claims of improved quality.
The National Highway Traffic Safety Administration stepped up its investigation into the trucks late last week, classifying it as an "engineering analysis" in a step that can precede a recall.
If deemed necessary, following GM's own report of 96 injuries linked to the tailgate problem, the recall would involve nearly 4.5 million of the pickups sold by the world's largest automaker, NHTSA said.
The trucks are 1999-2003 Chevrolet Silverados and GMC Sierras, as well as Chevrolet Avalanche and Cadillac EXT trucks from the 2002 and 2003 model years.
GM has reported 430 complaints about one or both of the tailgate support cables breaking on the trucks that are the target of NHTSA's investigation, the federal agency said.
It said GM had also reported more than 61,000 warranty claims due to the problem.
GM has recalled more than 2.4 million vehicles due to other potential safety problems this month. The recalls, though not uncommon for a mass market automaker, follow GM's recent assertions that its quality has rebounded from the dark days of the early 1990s when it almost went bankrupt.