"Complainants allege incidents of rollaway after the vehicle has been shifted to Park," NHTSA said in its problem description.
Federal safety regulators said they received 14 reports of unattended Grand Cherokees rolling away, resulting in five crashes and three injuries. There are no fatalities linked to the probe.
"The unintended motion has occurred with both the engine off and the engine running," NHTSA said.
It noted that the 2014-'15 Grand Cherokee is equipped with an electronic gear selector or shift-by-wire system. The gear selection is made by pressing the shifter-paddle forward or backwards. The shifter does not move along a gate path as with conventional gear selectors.
Fiat-Chrysler spokesman Eric Mayne told Edmunds that the automaker is "fully cooperating" with the investigation.
A preliminary evaluation has been opened to assess the scope, frequency and safety-related consequences of the alleged defect. Such an action sometimes precedes a vehicle recall.
NHTSA opened the investigation based on Vehicle Owners' Questionnaires, which are used with other complaints to determine if a safety-related defect trend exists.
Edmunds says: There is no recall at this point. Owners of these vehicles must wait for federal safety regulators to finish their investigation. If you have a concern in the meantime, it's best to contact your Jeep dealer now.