A truck mechanic, also known as a heavy-duty truck mechanic, is responsible for inspecting, diagnosing, repairing, and maintaining the mechanical and electrical systems of large commercial vehicles like trucks and buses, performing tasks like engine maintenance, brake adjustments, transmission repairs, and electrical system checks, ensuring the vehicles are roadworthy and meet safety standards by conducting routine maintenance and addressing any malfunctions that arise; often utilizing diagnostic tools and technical manuals to identify issues and complete repairs effectively.