Free ASE School Bus Electrical/Electronic Systems (S6) Test Practice Questions

Sample Practice Questions

Try these 10 sample questions from the ASE School Bus Electrical/Electronic Systems (S6) Test practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1How should a digital multimeter be connected to measure the voltage supplied to a school bus relay coil?

   1. A.In series with the coil, using the amperes input
   2. B.In parallel with the coil, using the voltage inputCorrect answer: B
   3. C.Across the disconnected coil, using the ohms range
   4. D.In series with the coil, using the voltage input

   Explanation: The manual states, "Voltage must be measured with the meter in parallel with the circuit." Connect across the coil using the voltage input. A series current connection measures a different quantity, and an unpowered resistance test does not measure supplied voltage.

   Reference: Fluke 78 Automotive Meter Users Manual — p. 14, How to Measure Voltage, step 3

2. 2A rested lead-acid bus battery has an apparently normal no-load terminal voltage. What can be concluded from that reading alone?

   1. A.Its cranking capacity has been verified under load
   2. B.Its internal condition is proven satisfactory
   3. C.Its state of charge is indicated, but condition is not establishedCorrect answer: C
   4. D.Its cable connections have passed a high-current test

   Explanation: Fluke states, "The no-load voltage only indicates the state of charge, not the condition of the battery." A separate suitable battery test is needed to assess performance. No-load voltage also does not establish high-current cable performance.

   Reference: Fluke 78 Automotive Meter Users Manual — p. 14, How to Measure Voltage, step 4

3. 3Using Delco Remy's specified 500 A cable test on a 12 V bus with a 42MT starter, positive cable drop is 0.35 V and negative cable drop is 0.25 V. What is the correct conclusion?

   1. A.The cables pass because neither individual drop exceeds 0.500 V
   2. B.Only the positive reading counts toward the cable-loss limit
   3. C.Total loss is 0.60 V; repair the excessive-drop cable circuitCorrect answer: C
   4. D.Total loss is 0.10 V; the starter must be replaced

   Explanation: The procedure says, "Add positive cable loss (V4) and negative cable loss (V5) to get total cable loss (V3)." For this 12 V 42MT application the maximum is 0.500 V. The sum is 0.60 V, so the excessive circuit loss must be corrected before condemning the starter.

   Reference: Delco Remy Diagnostic Procedures Manual for Starters and Alternators — p. 13, BATTERY CABLE TEST WITH SINGLE BATTERY LOCATION, Test: total positive-plus-negative cable loss and limits

4. 4A bus alternator charges intermittently because its otherwise serviceable drive belt slips at below-specified tension. Which correction addresses the identified drive fault?

   1. A.Increase regulator voltage to compensate for belt slip
   2. B.Keep the belt loose to avoid loading the alternator bearings
   3. C.Fit a higher-output alternator without correcting belt tension
   4. D.Adjust the belt to the manufacturer's specified tensionCorrect answer: D

   Explanation: DENSO explains, "If the drive belt is too loose, it will slip around the pulley causing the alternator to charge irregularly or not at all." Correct the identified tension defect. Raising regulator voltage or changing alternator capacity leaves the slipping drive uncorrected; retaining inadequate tension preserves it.

   Reference: DENSO Charging System Diagnosis — Helpful Tips, item 5, drive belt too loose

5. 5During a functional test of the C2 daytime-running-light system described in the manual, the ignition is on, the headlight switch is off, and the parking brake is applied. What change normally activates the DRLs?

   1. A.Turn the ignition off while keeping the parking brake applied
   2. B.Release the parking brake with the ignition remaining onCorrect answer: B
   3. C.Select high beams with the ignition switched off
   4. D.Turn on the headlights while keeping the parking brake applied

   Explanation: The manual specifies "Switching on the ignition and releasing the parking brakes" as the combination that activates the described DRL system. Applying the parking brake or switching on the headlights ends DRL operation. Safely controlling the bus remains necessary during this functional test.

   Reference: Saf-T-Liner C2 School Bus Driver's Manual — pp. 7.1–7.2, Daytime Running Lights

6. 6On the Blue Bird BBCV/D3/A3 instrumentation covered by the electrical troubleshooting table, all gauge pointers wag and errors are displayed. Which common condition does the table associate with this pattern?

   1. A.All senders are simultaneously reporting full-scale values
   2. B.The gauges are performing their normal startup check
   3. C.One sender's calibration alone has shifted to a new value
   4. D.The instrumentation is receiving no J1939 dataCorrect answer: D

   Explanation: The table identifies, "No J1939 data being received by instrumentation." This shared communications-failure pattern is not a normal completed startup sequence or one sender’s calibration error. Actual high sender values would drive readings, rather than establish the specified all-gauge communications-error pattern.

   Reference: Blue Bird Trouble Shooting Guidelines—Electrical — p. 1, All gauge pointers are wagging/errors displayed

7. 7A Blue Bird horn does not sound, and the specified horn feed has no 12 V when the horn is commanded. What diagnostic direction does the manufacturer prescribe?

   1. A.Replace the horn before tracing the supply circuit
   2. B.Trace the horn supply circuit using the wiring schematicCorrect answer: B
   3. C.Check only the horn ground connection and its resistance
   4. D.Check only the horn coil's resistance after disconnecting it

   Explanation: The guide says, "If no 12 volts at horns, check circuit per wiring schematic". Missing commanded supply requires tracing the supply circuit. Horn replacement, a ground-only test, or an isolated coil test does not locate the missing feed.

   Reference: Blue Bird Trouble Shooting Guidelines—Electrical — p. 2, Horn not working

8. 8A school bus circuit normally carries 35 A. Which method follows the Fluke 78 instructions for measuring this current?

   1. A.Place its 10 A input directly across the load
   2. B.Insert its 10 A input in series with the load
   3. C.Place its voltage input in series with the load
   4. D.Use a suitable DC current clamp on the conductorCorrect answer: D

   Explanation: Fluke instructs, "Always use clamp-on probes (dc current clamps) for circuits of more than 10 A." The 35 A load exceeds the meter input limit. A voltage input in series is not a current measurement, and connecting the current input across a load is improper.

   Reference: Fluke 78 Automotive Meter Users Manual — p. 18, How to Measure Current, Warning

9. 9A flooded bus battery rated at 900 CCA has passed the preliminary checks. In the Delco Remy half-CCA load test, what load and measurement time should be used?

   1. A.450 A, with voltage recorded after 15 seconds under loadCorrect answer: A
   2. B.900 A, with voltage recorded after 15 seconds under load
   3. C.450 A, with voltage recorded 15 seconds after removing the load
   4. D.300 A, with voltage recorded 60 seconds after removing the load

   Explanation: Delco Remy specifies a test load equal to half the battery’s CCA rating and directs, "After 15 seconds with load on, measure and record battery terminal voltage." Half of 900 CCA is 450 A. The reading is taken while the test load remains applied, not after voltage recovery.

   Reference: Delco Remy Diagnostic Procedures Manual for Starters and Alternators — p. 12, TEST PROCEDURE for conventional flooded batteries, Test: half-CCA load and terminal-voltage timing

10. 10A bus starter solenoid repeatedly pulls in and drops out. Battery-post voltage remains adequate under load, but voltage at the solenoid control terminal collapses as it pulls in and recovers when it releases. Which fault best explains this pattern?

    1. A.Excessive resistance in the solenoid control circuitCorrect answer: A
    2. B.Damaged teeth on the starter pinion drive
    3. C.A slipping starter overrunning clutch
    4. D.Starter-relay contacts welded in the closed position

    Explanation: Delco Remy states, "The starter shifting in and out, or not pulling in, is often caused by high resistance in the starter solenoid circuit." A resistive control path loses more voltage while supplying the energized coil, allowing dropout and recovery. Pinion teeth and the overrunning clutch concern mechanical torque transfer; welded closed contacts cause a retained command rather than this control-voltage loss.

    Reference: Delco Remy Diagnostic Procedures Manual for Starters and Alternators — p. 14, section 3-13, Starter Solenoid Circuit Test