Perform routine preventative maintenance on all vehicles, including oil and filter changes, equipment inspections, and thorough annual inspections on vehicles exceeding 24,000 pounds GVW, in accordance with Arizona Department of Transportation (ADOT) regulations, to ensure safety compliance and operational readiness, and conduct vehicle emissions testing to ensure compliance with state and federal environmental regulations. Inspect, diagnose, and perform complex repairs on heavy-duty vehicles and equipment, including engine systems, electrical/electronic components, braking, climate control, drivetrain, suspension, and body systems; test for proper operation and estimate repair time and cost.