Safety and Shop Practices
Safety underpins every other domain and is tested as knowledge you must apply, not recite. Know the hazards specific to diesel bus work: high-pressure fuel (injection injury), high-voltage hybrid/electrical systems, hot exhaust and coolant, rotating components, heavy components, and battery hydrogen. Understand lockout/tagout, proper lifting and blocking, PPE (eye/ear/hand protection), and ventilation for exhaust. Know that high-pressure fuel can penetrate skin - a medical emergency, not a minor cut.
Procedures: disconnect and isolate batteries (ground first) before electrical work; relieve fuel and cooling-system pressure before opening; support the vehicle with rated stands, never a jack alone; and use the correct lifting points. Handle DEF and coolant per spec and dispose of fluids properly. Keep the work area clean and control ignition sources near batteries and fuel.
Traps: working under a vehicle supported only by a jack; cracking high-pressure fuel lines to bleed (injury risk); leaving the master switch on during service; and ignoring hybrid high-voltage isolation. Also, treating a fuel-injection skin puncture as trivial. Fatigue and rushing cause shortcuts - the test rewards the safe procedure.
Rule of thumb: before any repair, ask "what stores energy here?" - pressure, voltage, heat, weight, or rotating mass - then isolate it. Ground disconnect first on 12/24 V; follow the OEM high-voltage isolation procedure on hybrid buses.
Worked example: A technician feels a sting while checking a high-pressure line. Correct action: stop work, seek immediate medical evaluation (injection injury can be serious even with a tiny wound), and report it - not "walk it off."