The engineering analysis probe covers 2010-2012 and 2014-2016 Equinox and Terrain vehicles. NHTSA could demand a recall after it completes the probe.
NHTSA said it has reviewed 1,900 complaints and reports related to the issue in the 1.7 million vehicles.
NHTSA said it has seen elevated failure rates in the 1.7 million vehicles, even though GM said the recalled vehicles have "double the warranty rate and five times the complaint rate."
GM said it will "fully cooperate to support their investigation. We do not believe these windshield washer systems are defective."
The wiper failures that prompted the 2016 recall were attributed to water and debris intrusion into the windshield wiper assembly ball joints, leading to excessive wear and eventual detachment of the ball joint.
GM said it was installing an improved windshield wiper motor and transmission assembly and relocating a drain hole at the base of the windshield.