ASE S2 Diesel Engines (School Bus) study guide
ASE S2 Diesel Engines (School Bus) · Work through your exam, one topic at a time.
ASE S2 Diesel Engines is one of the specialty credentials in the ASE School Bus certification series. It certifies that a technician can diagnose, adjust, and repair the diesel engines used in school bus applications, including the engine block and valve train, lubrication and cooling, air induction and exhaust, fuel injection and governing, engine braking and electronic controls, starting and charging, and emissions aftertreatment. The ASE S2 Diesel Engines (School Bus) study guide has 8 sections and about 2,806 words.
01General Engine Diagnosis
General diagnosis is the process of turning a customer complaint into a verified fault before any wrench moves. Know the difference between a symptom (what the driver reports), a condition (what you can measure), and a root cause (what actually failed).
372 words, about 2 min02Cylinder Head, Valve Train, and Engine Block Diagnosis and Repair
This domain covers the hard parts: head castings, valves, seats, guides, springs, pushrods, rockers, camshaft, lifters, liners, pistons, rings, bearings, and the block itself. You should understand valve adjustment procedures (overhead valve lash vs.
371 words, about 2 min03Lubrication and Cooling Systems Diagnosis and Repair
Lubrication and cooling protect the engine, and their failures often cause the mechanical faults tested in other domains. Know the oil system path: pan, pickup, pump, relief valve, filter, galleries, and turbo feed.
379 words, about 2 min04Air Induction and Exhaust Systems Diagnosis and Repair
Air induction and exhaust control how much air enters and how cleanly it leaves. Know the path: air cleaner, intake piping, turbocharger (compressor, turbine, wastegate or VGT), charge-air cooler, intake manifold, then exhaust manifold, turbo, DOC/DPF, SCR, and tailpipe.
358 words, about 2 min05Fuel System Diagnosis and Repair
The fuel system delivers the right quantity at the right time and pressure. Know the low-pressure side (tank, lift pump, filters, lines) and the high-pressure side (high-pressure pump, rail, injectors, return).
337 words, about 2 min06Engine Brakes, Retarders, and Engine Electrical/Electronic Systems Diagnosis and Repair
Engine brakes (compression release or exhaust brakes) and retarders help control vehicle speed on grades. Know how a compression-release brake works: it opens the exhaust valve near top dead center to release compressed air, and it depends on proper valve lash, oil pressure, and electrical signals.
331 words, about 2 min07Starting and Charging Systems Diagnosis and Repair
Starting and charging keep the diesel running and restarting. Know the starting circuit: batteries, cables, master switch, starter solenoid, starter motor, and the ECM's crank request.
330 words, about 2 min08Emissions Control Systems Diagnosis and Repair
Modern diesel emissions control includes EGR, DOC, DPF, SCR, and associated sensors and dosing systems. Know the purpose of each: EGR reduces NOx by lowering combustion temperature; DOC oxidizes CO and HC and helps regenerate the DPF; DPF traps soot and regenerates by heat; SCR uses DEF and a catalyst to reduce NOx.
328 words, about 2 min