(Reuters) - The National Highway Traffic Safety Administration said on Wednesday it has closed an investigation on Daimler Truck's 313,101 North American vehicles over an engine wiring concern.

The auto safety regulator had opened the probe, which covered Daimler's Freightliner Cascadia trucks from model years 2017-2021, on reports of engine electrical wiring harness chafe in certain vehicles.

The root cause was a combination of inadequate design clearance installation variability and motion between the wiring harness and the point of contact such as from vibration, it said.

The chafing could result in issues such as diagnostic fault codes, difficult or no engine start condition and reduced power or shut downs.

No safety-related defect trend has been identified, NHTSA said.