Jan 15 (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.