Free ASE School Bus Diesel Engines (S2) Practice Questions

Sample Practice Questions

Try these 10 sample questions from the ASE School Bus Diesel Engines (S2) practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1A school bus driver reports an intermittent loss of engine power on a particular grade. No immediate safety defect is found. What should the technician do before selecting a repair?

   1. A.Replace the fuel pump based on the reported loss of power.
   2. B.Road test under the reported conditions to verify the concern.Correct answer: B
   3. C.Clear diagnostic data to establish a fresh starting point.
   4. D.Adjust engine settings to compensate for the reported symptom.

   Explanation: ASE directs the technician to "Verify the complaint and road test". Reproducing the reported operating condition establishes what needs diagnosis before choosing a repair. A reported symptom alone does not identify a failed pump or justify changing settings; clearing data does not verify the complaint.

   Reference: Official ASE School Bus Study Guide — p. 9, Task A1

2. 2When installing a cylinder-head gasket under Elring's seven-step procedure, what should the technician do with additional sealing compound on the gasket?

   1. A.Coat both faces to supplement the factory coating.
   2. B.Apply it around every coolant opening.
   3. C.Install the gasket without additional sealing compound.Correct answer: C
   4. D.Apply it after the first stage of head-bolt tightening.

   Explanation: Elring specifies installation "without applying any additional sealing compound". Its coated head gasket is installed as directed, with the coating undamaged. Adding a coating or local sealant is not part of that procedure. Engine-specific installation instructions still apply.

   Reference: Elring — Cylinder-Head Gaskets: Everything for a Reliable Seal — p. 26, Professional installation, step 4

3. 3A school bus displays a low engine-oil-pressure warning. Before deciding that the oil pump has failed, what must the technician establish?

   1. A.Whether the actual oil pressure and its indicating circuit agree.Correct answer: A
   2. B.Whether clearing the warning leaves the oil level unchanged.
   3. C.Whether a higher-viscosity oil can hide the warning.
   4. D.Whether disconnecting the pressure sensor extinguishes the lamp.

   Explanation: ASE requires technicians to "Verify engine oil pressure" and check the pressure sensor/switch, connections, and gauge. The diagnostic question is whether the pressure itself is low or its reporting system is faulty. Hiding, clearing, or disconnecting a warning does not establish that distinction.

   Reference: Official ASE School Bus Study Guide — p. 10, Task C1

4. 4After replacing an air-cleaner element under the Freightliner manual-reset indicator procedure, what must be done to the restriction indicator?

   1. A.Leave its previous maximum reading latched.
   2. B.Disconnect its sensing line to prevent repeat warnings.
   3. C.Reset it after the element service.Correct answer: C
   4. D.Wait for another restriction indication before resetting it.

   Explanation: Freightliner specifies "Reset the air restriction indicator." This completes element service by clearing the retained indication. Leaving the old reading, disconnecting the sensing line, or postponing reset until another indication does not perform that service step.

   Reference: Freightliner Business Class M2 Plus Maintenance Manual — Replacement and Inspection of the Air Cleaner Element — Air Intake, final step after element inspection/replacement

5. 5A school bus fuel cap has a torn sealing gasket. Why should the defect be corrected even though no diesel is dripping from the cap?

   1. A.A dry cap proves the gasket still provides an adequate inward seal.
   2. B.A damaged cap seal can admit contaminants without an outward fuel leak.Correct answer: B
   3. C.The tank's vent makes the cap gasket unnecessary for contamination control.
   4. D.Fuel-pump suction prevents contaminants entering through a damaged gasket.

   Explanation: Cummins identifies "damaged caps, seals or gaskets" as contamination opportunities. An outwardly dry cap does not prove inward sealing; normal tank ventilation and pump suction do not make a damaged cap gasket acceptable.

   Reference: Cummins Diesel Fuel Contaminants — Micro-organisms, final paragraph

6. 6An adequately charged East Penn heavy-duty AGM battery is rated at 900 CCA. What adjustable test load does East Penn specify for its BCI load-test procedure?

   1. A.225 A
   2. B.300 A
   3. C.450 ACorrect answer: C
   4. D.900 A

   Explanation: East Penn specifies "½ the CCA rating". Half of 900 CCA is a 450 A load. The other values use an incorrect fraction or the full rating.

   Reference: East Penn AGM Batteries in Heavy-Duty Truck Applications — Page 4, C. BCI and Fixed Load Test Procedure, step 2

7. 7An intermittent school bus engine complaint cannot yet be reproduced. How should the technician use the available driver report and past maintenance records?

   1. A.Compare the reported operating conditions with previous maintenance and repairs.Correct answer: A
   2. B.Use the driver report but exclude prior repairs because they are already completed.
   3. C.Use past maintenance records but disregard the driver's account until a code is stored.
   4. D.Set both records aside because the complaint is absent during the initial inspection.

   Explanation: ASE calls for technicians to "review the driver report" and available past maintenance documents. Together they establish operating conditions and prior work relevant to the complaint; an intermittent symptom or lack of a stored code does not make either record irrelevant.

   Reference: Official ASE School Bus Study Guide — p. 9, Task A1

8. 8An engine manufacturer permits cylinder-head bolt reuse subject to specified inspection and tightening instructions. Which approach is consistent with Elring's explanation of this exception?

   1. A.Measure bolt expansion and follow the applicable reuse instructions.Correct answer: A
   2. B.Reuse the bolts whenever their threads look clean.
   3. C.Retighten to the original torque without checking expansion.
   4. D.Use the amount of loosening torque as the only reuse criterion.

   Explanation: Elring explains that, where the manufacturer allows reuse, the "rate of expansion must be measured" and modified tightening instructions may apply. Visual thread condition or loosening torque alone does not establish acceptable elongation. Elring generally recommends new bolts; the question expressly concerns a manufacturer-authorized exception.

   Reference: Elring — Cylinder-Head Bolts — Did you know? Is a reuse of old head bolts allowed?

9. 9According to BF's general service guidance, how are its engine oil pumps normally renewed when replacement is needed?

   1. A.By mixing used gears from different pump assemblies.
   2. B.By resurfacing every pump housing regardless of wear limits.
   3. C.As a complete pump unit rather than reconditioning it.Correct answer: C
   4. D.By replacing only the drive gear regardless of internal wear.

   Explanation: BF says its oil pumps are generally renewed as complete units and are "not intended to be reconditioned." This supplier guidance rejects mixing used gears, indiscriminate resurfacing, or renewing only a drive gear as a substitute for replacement of the worn pump unit.

   Reference: BF — Products in Focus — p. 14, Oil pumps in Focus

10. 10On a Freightliner school bus chassis covered by MOP 09–02, the specified air-cleaner replacement interval has arrived, although restriction remains below the engine's limit. What does this maintenance instruction require?

    1. A.Keep the element until both the interval and restriction limit are exceeded.
    2. B.Replace the element at the recommended interval.Correct answer: B
    3. C.Extend the interval solely because the restriction reading is low.
    4. D.Use a higher restriction limit to decide when the interval applies.

    Explanation: The manual specifies replacement at the "recommended interval", or when the restriction threshold is reached. These are alternative triggers. A below-limit restriction reading therefore does not cancel the scheduled replacement requirement.

    Reference: Freightliner School Bus Chassis Maintenance Manual — 09/1, MOP 09–02, Air Cleaner Element Replacing