100+ Free ASE S2 Diesel Engines (School Bus) Practice Questions
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A school bus diesel fuel system has water contamination. The MOST likely consequences are:
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Key Facts: ASE S2 Diesel Engines (School Bus) Exam
65 / 55
Total / Scored Questions
ASE School Bus (S Series) test information
90 min
Testing Time
ASE S2 test information
~$59
Test Fee (ASE registration)
ASE registration
Criterion-referenced
Scoring Method
ASE scoring policy
27 / 11 / 13 / 16 / 27 / 6
Official Content Area Weights
ASE S2 content area blueprint
2 years
Required Work Experience
ASE certification requirements
ASE lists the S2 School Bus Diesel Engines test as 65 total questions with 55 scored multiple-choice items in 90 minutes, delivered through Prometric and graded with criterion-referenced scoring. The official content areas are weighted General Engine Diagnosis 27%, In-Chassis Engine Inspection & Repair 11%, Lubrication & Cooling Systems 13%, Air Induction & Exhaust Systems 16%, Fuel System 27%, and Starting System 6%. Certification also requires two years of relevant work experience, with training substitutable for up to one year.
Sample ASE S2 Diesel Engines (School Bus) Practice Questions
Try these sample questions to test your ASE S2 Diesel Engines (School Bus) exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.
1A school bus with a Cummins ISB diesel engine cranks normally but will not start, and the technician confirms there is no fuel reaching the high-pressure pump. Which check should be performed FIRST?
2Technician A says low engine compression on one cylinder can cause hard starting and a miss. Technician B says a cylinder cutout (power balance) test can help isolate a weak cylinder on an electronically controlled diesel. Who is correct?
3A school bus diesel produces excessive black smoke under acceleration but idles cleanly. The MOST likely cause is:
4During a cylinder compression test on a school bus diesel, one cylinder reads significantly lower than the others. Adding a small amount of oil through the injector bore raises that cylinder's reading noticeably. This indicates:
5A school bus engine has low power and the ECM logs no active fault codes. The technician should:
6Blue-gray smoke from the exhaust of a school bus diesel, most noticeable at startup and during deceleration, MOST likely indicates:
7A cylinder leakage (leak-down) test on a school bus diesel shows air escaping from the engine oil fill/crankcase. This indicates a leak past the:
8A school bus diesel has a steady knock that increases with engine speed and is loudest at light load, with no related fault codes. The technician should suspect:
9Technician A says white smoke at cold start that clears as the engine warms can be normal unburned fuel from cold combustion. Technician B says continuous white smoke with a sweet odor and coolant loss indicates coolant entering the combustion chamber. Who is correct?
10A school bus engine is consuming engine oil but shows no external leaks and the exhaust shows blue smoke under load. Compression is good. The MOST likely cause is:
About the ASE S2 Diesel Engines (School Bus) Exam
ASE S2 — Diesel Engines (School Bus) is the National Institute for Automotive Service Excellence certification test covering diagnosis and repair of school-bus diesel engines. It tests general engine diagnosis, in-chassis engine inspection and repair, lubrication and cooling systems, air induction and exhaust (including aftertreatment), fuel systems, and starting systems on modern school-bus diesels.
Assessment
55 scored multiple-choice (65 total incl. 10 unscored) (official ASE); this practice bank is 100 selected-response items
Time Limit
90 minutes
Passing Score
Criterion-referenced (set by ASE)
Exam Fee
~$59 (ASE registration) (ASE (National Institute for Automotive Service Excellence))
ASE S2 Diesel Engines (School Bus) Exam Content Outline
General Engine Diagnosis
Complaint verification and isolation for hard-start/no-start, low power, smoke colors, knocks, and oil/coolant consumption using fault codes, freeze-frame, live data, compression, cylinder leakage, cylinder cutout, and oil/coolant analysis.
In-Chassis Engine Inspection & Repair
In-chassis cylinder head, gasket, valvetrain, injector, liner, and seal service including torque sequences, torque-to-yield fasteners, surface flatness, valve lash, and valvetrain timing verification.
Lubrication & Cooling Systems Diagnosis & Repair
Oil pressure and contamination diagnosis, oil cooler and filter service, thermostat and water pump, radiator and fan-clutch cooling capacity, extended-life coolant and SCA chemistry, and cylinder liner cavitation prevention.
Air Induction & Exhaust Systems Diagnosis & Repair
Air filter restriction, turbocharger and VGT operation, charge air cooler and boost leaks, EGR cooler, DOC/DPF/SCR/DEF aftertreatment, regeneration on the school-bus duty cycle, exhaust back pressure, and exhaust integrity safety.
Fuel System Diagnosis & Repair
Low- and high-pressure fuel supply, common-rail/HEUI/unit injectors, rail pressure performance, injector return/back-leakage, injector calibration coding, water and gelling contamination, priming, and cylinder fueling balance.
Starting System Diagnosis & Repair
Battery condition, voltage-drop and starter current-draw testing, starter drive and ring gear, starter control circuit and start interlocks, and cold-start aids for school-bus diesel cranking.
How to Pass the ASE S2 Diesel Engines (School Bus) Exam
What You Need to Know
- Passing score: Criterion-referenced (set by ASE)
- Assessment: 55 scored multiple-choice (65 total incl. 10 unscored) (official ASE); this practice bank is 100 selected-response items
- Time limit: 90 minutes
- Exam fee: ~$59 (ASE registration)
Keys to Passing
- Complete 500+ practice questions
- Score 80%+ consistently before scheduling
- Focus on highest-weighted sections
- Use our AI tutor for tough concepts
ASE S2 Diesel Engines (School Bus) Study Tips from Top Performers
Frequently Asked Questions
How many questions are on the ASE S2 test?
ASE lists the S2 School Bus Diesel Engines test as 65 total questions, of which 55 are scored multiple-choice items and 10 are unscored research questions. This free practice bank provides 100 selected-response items aligned to the six official S2 content areas.
How much time and what does ASE S2 cost?
The S2 test allows 90 minutes of testing time. The test fee is approximately $59 through ASE registration, in addition to any ASE registration administration fee; confirm the current amount when you register at ase.com.
What is the passing score for ASE S2?
ASE uses criterion-referenced scoring rather than a fixed percentage. The passing standard is set by ASE based on the difficulty of the form, so there is no single published percentage that applies to every test session.
What are the official ASE S2 content areas and weights?
ASE weights S2 as General Engine Diagnosis 27%, In-Chassis Engine Inspection & Repair 11%, Lubrication & Cooling Systems 13%, Air Induction & Exhaust Systems 16%, Fuel System 27%, and Starting System 6%. General Engine Diagnosis and Fuel System are the two largest areas.
What experience do I need to be ASE S2 certified?
Passing the test plus two years of relevant hands-on work experience is required for certification. Relevant formal training can substitute for up to one year of the experience requirement per current ASE policy, and you submit experience documentation to ASE after passing.
Are there Technician A / Technician B questions on ASE S2?
Yes. Like other ASE tests, S2 uses the Technician A / Technician B format along with standard multiple-choice and EXCEPT-style items. This practice bank includes Technician A/Technician B questions so you can practice that reasoning style.