A burned fusible link is replaced. How is a fusible link typically sized against the wire it protects?Wikipedia, Fusible link, Electrical. ASE S6 content area A, General Electrical/Electronic System Diagnosis (6 of 45 questions)
A data bus fault is traced on a CAN network. What terminates each end of the bus?Wikipedia, CAN bus, Physical layer. ASE S6 content area A, General Electrical/Electronic System Diagnosis (6 of 45 questions)
A key-off drain shows on the ammeter with everything switched off. Circuits are isolated one at a time. Which circuit holds the fault?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Battery Drain Test. ASE S6 content area A, General Electrical/Electronic System Diagnosis (6 of 45 questions)
A multimeter is switched to a current range. How is it connected, and what does it add to the circuit?Wikipedia, Multimeter, Burden voltage. ASE S6 content area A, General Electrical/Electronic System Diagnosis (6 of 45 questions)
An oscilloscope on a blower control wire shows a rectangular wave whose on-time widens as the fan speeds up. What is this kind of signal used to control?Wikipedia, Pulse-width modulation, opening section. ASE S6 content area A, General Electrical/Electronic System Diagnosis (6 of 45 questions)
Most lamps and motors on a bus work, yet certain electronic circuits do not. Which battery fault does the Navy manual connect with that?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Troubleshooting Lighting Systems and Electrical Accessories. ASE S6 content area A, General Electrical/Electronic System Diagnosis (6 of 45 questions)
Show all 45 questions (39 more)
Low-voltage battery 4
A spare bus is left on a maintenance charger all summer. Which battery chemistry cannot handle indefinite trickle charging?Wikipedia, Battery charger, Trickle charger. ASE S6 content area B, Low-Voltage Battery Diagnosis and Service (4 of 45 questions)
Battery posts are cleaned of corrosion at every service on a flooded battery. What advantage does TM 9-8000 give for a sealed battery here?US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 12-8. ASE S6 content area B, Low-Voltage Battery Diagnosis and Service (4 of 45 questions)
How does an absorbed glass mat (AGM) battery differ from a flooded lead-acid battery?Wikipedia, VRLA battery, Absorbent glass mat (AGM). ASE S6 content area B, Low-Voltage Battery Diagnosis and Service (4 of 45 questions)
On a very cold morning a discharged battery is found frozen. What should be done about jump starting?Wikipedia, Jump start (vehicle), Procedures. ASE S6 content area B, Low-Voltage Battery Diagnosis and Service (4 of 45 questions)
Starting system 6
A bus has over-crank protection in its starter control circuit. Why is cranking time limited?Wikipedia, Starter (engine), Electric. ASE S6 content area C, Starting System Diagnosis and Repair (6 of 45 questions)
A starter solenoid sticks and holds the pinion in mesh after the engine fires. What keeps the engine from driving the starter motor?Wikipedia, Starter (engine), Electric. ASE S6 content area C, Starting System Diagnosis and Repair (6 of 45 questions)
Cranking voltage reads lower than specified. What does the Navy manual test next?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Cranking Voltage Test. ASE S6 content area C, Starting System Diagnosis and Repair (6 of 45 questions)
In the starter current draw test of the Navy manual, the cranking voltage is noted. After cranking, how is the current found?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Starting Motor Current Draw Test. ASE S6 content area C, Starting System Diagnosis and Repair (6 of 45 questions)
The solenoid switch (control) circuit is tested while cranking. Unless the maker says otherwise, what voltage loss should it not exceed?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Solenoid Switch Circuit Resistance Test. ASE S6 content area C, Starting System Diagnosis and Repair (6 of 45 questions)
The voltmeter is placed across one starter cable of a 12-volt system while cranking. What is the most it should read?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Starter Insulated Circuit Resistance Test. ASE S6 content area C, Starting System Diagnosis and Repair (6 of 45 questions)
Charging system 7
A charging system insulated circuit resistance test is set up on an alternator (ac) system. What load current does the Navy manual set?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Charging System Insulated Circuit Resistance Test. ASE S6 content area D, Low-Voltage Charging System Diagnosis and Repair (7 of 45 questions)
A replacement alternator has a Y-connected stator where the old one was delta-connected. How do the two differ in output?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Alternators. ASE S6 content area D, Low-Voltage Charging System Diagnosis and Repair (7 of 45 questions)
How does a transistor regulator limit alternator voltage, by the Navy manual?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Regulators. ASE S6 content area D, Low-Voltage Charging System Diagnosis and Repair (7 of 45 questions)
On the scope, the alternator ripple shows a high and low peak every sixth pulse with no break in rectification. What does the Navy manual read from that?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Weak Diodes. ASE S6 content area D, Low-Voltage Charging System Diagnosis and Repair (7 of 45 questions)
One alternator diode has stopped conducting. Which instrument does the Navy manual say shows the fault easily when an ammeter or voltmeter may not?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Charging Circuit Diodes. ASE S6 content area D, Low-Voltage Charging System Diagnosis and Repair (7 of 45 questions)
The ripple pattern of alternator output disappears from the scope screen entirely. Which fault does that, by the Navy manual?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Charging Circuit Diodes. ASE S6 content area D, Low-Voltage Charging System Diagnosis and Repair (7 of 45 questions)
What usually becomes of a shorted alternator diode or shorted winding left in service, by the Navy manual?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Open and Shorted Diodes. ASE S6 content area D, Low-Voltage Charging System Diagnosis and Repair (7 of 45 questions)
Lighting and warning lamp systems 12
A pure tone back-up alarm is bench tested. About what tone and loudness do such models produce?Wikipedia, Back-up beeper, opening section. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
A roof accessory is mounted near the rear school bus signal lamps. Within what area must the signal of those lamps stay unobstructed, under FMVSS 108?49 CFR 571.108, Table V-a. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
A stop arm flasher is replaced. What share of the flash cycle must the current "on" time of ordinary stop arm lamps be, under FMVSS 131?49 CFR 571.131, S6.2.2.1. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
A stop arm override circuit has a timer on its audible signal. For how long must the timer make the signal sound, under FMVSS 131?49 CFR 571.131, S5.5. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
A stop arm with a lighted STOP legend is being repaired. Which lamp color may light the legend, under FMVSS 131?49 CFR 571.131, S5.3.1.1. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
A turn signal lamp has failed. How must the turn signal pilot indicator show it, under FMVSS 108?49 CFR 571.108, S9.3.6. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
A turn signal pilot indicator inside the bus is replaced with an LED. What color must it emit, under FMVSS 108?49 CFR 571.108, S9.3.4.1. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
A turn signal switch in the steering column tests bad and must come out. What usually has to be removed first, by the Navy manual?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Directional Signals. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
A xenon strobe light on the roof is opened for repair. Why is its capacitor treated with care?Wikipedia, Strobe light, Scientific explanation of flashtubes. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
The hazard warning switch is built into the turn signal lever assembly. What does FMVSS 108 require of the two controls?49 CFR 571.108, S9.6.1. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
The headlights work on low beam and will not change to high beam. Which part does the Navy manual go to?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Headlights. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
Xenon strobe lamps are fitted to a stop signal arm. What "off" time must they have before each flash, under FMVSS 131?49 CFR 571.131, S6.2.2.2. ASE S6 content area E, Lighting Systems Diagnosis and Repair (12 of 45 questions)
Gauges and warning devices 4
A dash dimmer is being tested. Which telltales may never be dimmed to an invisible level, under FMVSS 101?49 CFR 571.101, S5.3.3. ASE S6 content area F, Gauges and Instrument Warning Devices Diagnosis and Repair (4 of 45 questions)
A mechanical speedometer and odometer stop working together. How is the unit driven, by TM 9-8000?US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 17-6. ASE S6 content area F, Gauges and Instrument Warning Devices Diagnosis and Repair (4 of 45 questions)
A telltale lights briefly at key-on with no fault present. When may a telltale emit light, under FMVSS 101?49 CFR 571.101, S5.3.1. ASE S6 content area F, Gauges and Instrument Warning Devices Diagnosis and Repair (4 of 45 questions)
Why is a temperature warning light often fitted as well as a temperature gauge, by TM 9-8000?US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 17-5. ASE S6 content area F, Gauges and Instrument Warning Devices Diagnosis and Repair (4 of 45 questions)
Horn, wipers and other circuits 6
A heater blower motor circuit is traced for overheated wiring. How does burned insulation show itself, by the Navy manual?US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Small Accessory Motors. ASE S6 content area G, Miscellaneous (6 of 45 questions)
A horn adjusting nut is turned to raise the volume and the horn begins to sputter. What has happened, by TM 9-8000?US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 17-9. ASE S6 content area G, Miscellaneous (6 of 45 questions)
A two-speed wiper motor is tested after its resistor is replaced. By how much must the highest and one lower wiper speed differ, under FMVSS 104?49 CFR 571.104, S4.1.1.3. ASE S6 content area G, Miscellaneous (6 of 45 questions)
Cruise control drops out whenever the selector lever is moved. Why does the transmission control unit report the lever position to the cruise control?Wikipedia, Transmission control unit, Cruise control module. ASE S6 content area G, Miscellaneous (6 of 45 questions)
The horn and the airbag lamp fail together after steering column work. Which part carries those circuits to the turning steering wheel?Wikipedia, Clockspring, In automotive systems. ASE S6 content area G, Miscellaneous (6 of 45 questions)
What do advanced driver assistance systems (ADAS) use to detect obstacles or driver errors?Wikipedia, Advanced driver-assistance system, opening section. ASE S6 content area G, Miscellaneous (6 of 45 questions)
How this list was compiled: Our own questions, written to the test specifications and task list for Electrical/Electronic Systems (Test S6) in the ASE School Bus Study Guide (https://ase.com/wp-content/uploads/ASE_SchoolBus_Study_Guide.pdf, copyright 2026, read 2026-10-13): A general electrical/electronic system diagnosis 6 questions, B low-voltage battery diagnosis and service 4, C starting system diagnosis and repair 6, D low-voltage charging system diagnosis and repair 7, E lighting systems diagnosis and repair 12, F gauges and instrument warning devices diagnosis and repair 4, G miscellaneous 6; total 45. The bank holds the same 6, 4, 6, 7, 12, 4 and 6. Each fact was read on 2026-10-13 in the public text named under its question: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4; 49 CFR 571.101, 571.104, 571.108 and 571.131 (FMVSS 101, 104, 108 and 131) at ecfr.gov; US Army TM 9-8000, Principles of Automotive Vehicles (1985), chapters 12 and 17; and Wikipedia for meters, data networks, batteries and chargers, the starter, strobe lights, back-up alarms, the clockspring and driver assistance systems. The sample questions printed in the study guide were not used. Licence: Questions, choices and explanations are original work of this site.
How it works
This free ASE S6 school bus electrical electronic systems practice test has 45 questions of our own across the seven content areas ASE scores. The page is unofficial: the National Institute for Automotive Service Excellence (ASE) did not write, review or endorse it.
Read the full guide
Seven areas, lighting the largest
ASE scores 45 questions: general diagnosis 6, battery 4, starting 6, charging 7, lighting 12, gauges and warning devices 4, and miscellaneous 6. Lighting leads, and in S6 it takes in stop arm lamps and eight-lamp warning systems.
Rules for the lamps, a manual for the tests
Stop arm flash timing, lamp visibility, turn signal indicators and telltales are from Federal Motor Vehicle Safety Standards 131, 108 and 101. Voltage drop and scope tests come from a 1992 Navy manual. Meters, networks and batteries rest on Wikipedia.
What is left out
High-voltage systems of electric buses and a body builder's multiplex wiring are in no public source that could be checked, so the bank asks nothing about them.
For lighting, learn what FMVSS 131 and 108 require of stop arm and warning lamps.
Voltage drop limits are small: tenths of a volt across a cable or a switch while the starter cranks.
Questions and answers
How many questions are on the ASE S6 test?
Fifty-five in 90 minutes, of which 45 are scored, by ASE's 2026 School Bus study guide. Recertification is 23 questions in 45 minutes.
What does the ASE S6 test cover?
Diagnosis with a meter and a scope, low-voltage batteries, starting and charging, lighting with eight-lamp warning systems, stop arms and crossing gates, gauges and warning devices, and circuits such as horns, wipers, door controls and driver assistance systems.
Is ASE S6 required for Master School Bus Technician?
Yes. S6 is starred in ASE's study guide together with S2, S3, S4 and S5. Those five tests are required for ASE Certified Master School Bus Technician status.