For the electrical wiring between the frame and the body located on the front of the cab, the sheath of the harness does not have sufficient durability against up and down movements of the vehicle body at a low temperature, and therefore, vehicle vibration etc. during driving can cause a crack in the sheath. If this problem is left unattended, the sheath may break, which can result in corrosion of the wire core and disconnection of the wiring. At worst, the lights will not illuminate, and/or the engine stops and will not restart.