(Reuters) – The National Highway Traffic Safety Administration said on Wednesday it was closing an investigation into Daimler (OTC: ) 313,101 North American Truck vehicles due to concerns about engine wiring.

The auto safety regulator opened a probe, covering Daimler’s Freightliner Cascadia trucks from model years 2017-2021, into reports of engine electrical wiring harness chafe in some vehicles.

The reason is a combination of insufficient clearance design to install the difference and movement between the wiring harness and the point of contact such as from vibration, it said.

Chafing can result in issues such as diagnostic fault codes, difficult or no engine start conditions and reduced power or shutdown.

There is no known safety-related defect trend, NHTSA said.