• 68 questions

ASE Transit Bus Study Guide

Unofficial practice for the eight ASE transit bus tests, H1 to H8, every answer with its federal rule or manual.

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What is the lowest air compressor governor cut-in pressure FMVSS 121 allows for a bus?

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ASE transit bus tests: questions and time limits

TestQuestionsTime limitScored questionsRecertification testMaster statusCheckedSourceOfficial practice test
H1 Compressed Natural Gas (CNG) Engines6075 minutes50. The other 10 are not counted.25 questions in 30 minutes.H1 or H2 is needed, with H3 to H8.October 8, 2026ASE study guide (2026)ASE's own page for tests H1 to H8
H2 Diesel Engines6075 minutes50. The other 10 are not counted.25 questions in 30 minutes.H1 or H2 is needed, with H3 to H8.October 8, 2026ASE study guide (2026)ASE's own page for tests H1 to H8
H3 Drive Train5060 minutes40. The other 10 are not counted.20 questions in 30 minutes.Required.October 8, 2026ASE study guide (2026)ASE's own page for tests H1 to H8
H4 Brakes6075 minutes50. The other 10 are not counted.25 questions in 30 minutes.Required.October 8, 2026ASE study guide (2026)ASE's own page for tests H1 to H8
H5 Suspension and Steering5575 minutes45. The other 10 are not counted.23 questions in 30 minutes.Required.October 8, 2026ASE study guide (2026)ASE's own page for tests H1 to H8
H6 Electrical/Electronic Systems6090 minutes50. The other 10 are not counted.25 questions in 45 minutes.Required.October 8, 2026ASE study guide (2026)ASE's own page for tests H1 to H8
H7 Heating, Ventilation and Air Conditioning5075 minutes40. The other 10 are not counted.20 questions in 45 minutes.Required. Not an EPA Section 609 credential.October 8, 2026ASE study guide (2026)ASE's own page for tests H1 to H8
H8 Preventive Maintenance and Inspection6075 minutes50. The other 10 are not counted.25 questions in 30 minutes.Required.October 8, 2026ASE study guide (2026)ASE's own page for tests H1 to H8

Next step Air brake rules: CDL air brakes practiceASE automobile tests A1 to A8

All 68 questions with answers

H1 Compressed natural gas engines 9

  • How often must the label on a CNG fuel container say it should be visually inspected when it is installed on a vehicle with a GVWR over 10,000 pounds (4,536 kg)? Answer: At least every 12 months. Source: 49 CFR 571.304 (FMVSS 304, Compressed natural gas fuel container integrity), S7.4, Labeling. Outline: ASE Transit Bus Study Guide (copyright 2026), Compressed Natural Gas (CNG) Engines (Test H1), content area F, Fuel System Inspection, Diagnosis, and Repair.
  • In a distributorless ignition system, what tells the control unit which coil to fire and when? Answer: A crankshaft or camshaft sensor. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Distributorless ignition system. Outline: ASE Transit Bus Study Guide (copyright 2026), Compressed Natural Gas (CNG) Engines (Test H1), content area H, Ignition System Inspection, Diagnosis, and Repair.
  • In FMVSS 304, what is the service pressure of a CNG fuel container? Answer: The settled pressure at 21 °C (70 °F) with full gas content. Source: 49 CFR 571.304 (FMVSS 304, Compressed natural gas fuel container integrity), S4, Definitions. Outline: ASE Transit Bus Study Guide (copyright 2026), Compressed Natural Gas (CNG) Engines (Test H1), content area F, Fuel System Inspection, Diagnosis, and Repair.
Show all 68 questions (65 more)

H1 Compressed natural gas engines, continued

  • Under FMVSS 303, where is a CNG vehicle labeled with its service pressure? Answer: Near the vehicle refueling connection. Source: 49 CFR 571.303 (FMVSS 303, Fuel system integrity of compressed natural gas vehicles), S5.3, Labeling. Outline: ASE Transit Bus Study Guide (copyright 2026), Compressed Natural Gas (CNG) Engines (Test H1), content area F, Fuel System Inspection, Diagnosis, and Repair.
  • What does a vacuum gauge connected to the intake manifold of a spark-ignited engine measure? Answer: Manifold pressure compared with the atmosphere. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 17-8, Vacuum Gage. Outline: ASE Transit Bus Study Guide (copyright 2026), Compressed Natural Gas (CNG) Engines (Test H1), content area A, General Engine Diagnosis.
  • What drives a turbocharger? Answer: The force of the engine exhaust stream. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 4-30, Turbochargers. Outline: ASE Transit Bus Study Guide (copyright 2026), Compressed Natural Gas (CNG) Engines (Test H1), content area E, Air Induction and Exhaust Systems Diagnosis and Repair.
  • What must every CNG fuel container be equipped with under FMVSS 304? Answer: A pressure relief device. Source: 49 CFR 571.304 (FMVSS 304, Compressed natural gas fuel container integrity), S7.3, Bonfire test. Outline: ASE Transit Bus Study Guide (copyright 2026), Compressed Natural Gas (CNG) Engines (Test H1), content area F, Fuel System Inspection, Diagnosis, and Repair.
  • Why is an engine oil cooler fitted to an engine in heavy-duty service? Answer: Normal airflow cannot carry enough heat away from the oil. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 8-14, Oil Coolers. Outline: ASE Transit Bus Study Guide (copyright 2026), Compressed Natural Gas (CNG) Engines (Test H1), content area D, Lubrication and Cooling Systems Diagnosis and Repair.
  • Why should a series-wound starter motor never be run free with no load? Answer: It can build up enough speed to destroy itself. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 14-3, Automotive Starting Motor. Outline: ASE Transit Bus Study Guide (copyright 2026), Compressed Natural Gas (CNG) Engines (Test H1), content area G, Starting and Charging System Diagnosis and Repair.

H2 Diesel engines 9

  • A diesel engine knocks at light load. What is the cause of this knock, by TM 9-8000? Answer: Ignition lag: fuel builds up, then ignites all at once. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 5-5, Knocking. Outline: ASE Transit Bus Study Guide (copyright 2026), Diesel Engines (Test H2), content area A, General Engine Diagnosis.
  • Carbon has formed on the tips of the injector nozzles. What is the effect? Answer: The spray pattern is disrupted. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 5-2, Cleanliness and Stability. Outline: ASE Transit Bus Study Guide (copyright 2026), Diesel Engines (Test H2), content area F, Fuel System Diagnosis and Repair.
  • In the API oil classifications listed in TM 9-8000, which letters mark an oil for diesel engines? Answer: CA, CB, CC and CD. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 8-5, American Petroleum Institute rating system. Outline: ASE Transit Bus Study Guide (copyright 2026), Diesel Engines (Test H2), content area D, Lubrication and Cooling Systems Diagnosis and Repair.
  • Technician A says raising the compression ratio of a diesel engine reduces its tendency to knock. Technician B says raising the compression ratio of a gasoline engine reduces its tendency to knock. Who is right? Answer: Technician A only. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 5-5, Knocking. Outline: ASE Transit Bus Study Guide (copyright 2026), Diesel Engines (Test H2), content area A, General Engine Diagnosis.
  • What does the cetane number of a diesel fuel measure? Answer: Its ignition quality. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 5-4, Ignition Quality. Outline: ASE Transit Bus Study Guide (copyright 2026), Diesel Engines (Test H2), content area A, General Engine Diagnosis.
  • What does the delivery valve of an injection pump prevent when it closes? Answer: Fuel draining back, which could lose the prime. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), chapter 5, Multiple unit injection (delivery valve). Outline: ASE Transit Bus Study Guide (copyright 2026), Diesel Engines (Test H2), content area F, Fuel System Diagnosis and Repair.
  • What is an oil pressure lockout circuit in a starting system for? Answer: To keep the starter from being engaged on a running engine. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 14-8, Oil Pressure Lockout Circuit. Outline: ASE Transit Bus Study Guide (copyright 2026), Diesel Engines (Test H2), content area G, Starting and Charging System Diagnosis and Repair.
  • What is combined in the single housing of a unit injector? Answer: The injection pump, the fuel valves and the nozzle. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 5-17, Unit Injection System. Outline: ASE Transit Bus Study Guide (copyright 2026), Diesel Engines (Test H2), content area F, Fuel System Diagnosis and Repair.
  • Why does an ether injection system help a diesel engine start in cold weather? Answer: Ether is very volatile and vaporizes readily in the cold. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 5-33, Ether Injection System. Outline: ASE Transit Bus Study Guide (copyright 2026), Diesel Engines (Test H2), content area E, Air Induction and Exhaust Systems Diagnosis and Repair.

H3 Drive train 7

  • A clutch pack is applied with too little pressure and locks up too slowly on each shift. What happens to it in time? Answer: It slips too much, and the heat burns and ruins the clutches. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 7, Hydraulic system operation. Outline: ASE Transit Bus Study Guide (copyright 2026), Drive Train (Test H3), content area A, Automatic Transmission Diagnosis and Repair.
  • A drive shaft runs lengthways under the passenger floor of a bus. What does 49 CFR 393.89 require at the end of the shaft that has the sliding (spline) connection? Answer: A guard or bracket to stop the shaft whipping if it fails. Source: 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation), section 393.89, Buses, driveshaft protection. Outline: ASE Transit Bus Study Guide (copyright 2026), Drive Train (Test H3), content area B, Drive Shaft and Universal Joint Diagnosis and Repair.
  • As turbine speed nears pump speed, the stator roller clutch releases and the stator turns freely. What is the torque converter doing now? Answer: Acting as a fluid coupling with no torque multiplication. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 7, Torque converter operation. Outline: ASE Transit Bus Study Guide (copyright 2026), Drive Train (Test H3), content area A, Automatic Transmission Diagnosis and Repair.
  • In a hydraulically controlled automatic transmission, what supplies the vehicle speed signal for an upshift? Answer: The governor, driven by the output shaft. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 7, Hydraulic system operation. Outline: ASE Transit Bus Study Guide (copyright 2026), Drive Train (Test H3), content area A, Automatic Transmission Diagnosis and Repair.
  • In a simple planetary gearset the sun gear is held and power is applied to the internal (ring) gear. What is the result at the carrier? Answer: Reduction: lower speed and higher torque. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 7, Planetary gears. Outline: ASE Transit Bus Study Guide (copyright 2026), Drive Train (Test H3), content area A, Automatic Transmission Diagnosis and Repair.
  • On a transmission with a vacuum modulator, what does low engine vacuum signal? Answer: High torque, so modulator pressure is high. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 7, Hydraulic system operation (modulator). Outline: ASE Transit Bus Study Guide (copyright 2026), Drive Train (Test H3), content area A, Automatic Transmission Diagnosis and Repair.
  • Which is true of the axle shafts of a full-floating drive axle? Answer: They can be removed without removing the wheels. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 11, Full-floating axles. Outline: ASE Transit Bus Study Guide (copyright 2026), Drive Train (Test H3), content area C, Drive Axle Diagnosis and Repair.

H4 Brakes 9

  • A drive axle is overfilled with gear lubricant. What can the excess do at the wheel ends? Answer: Get past the wheel bearings and make the brakes slip or grab. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 11, Service and maintenance. Outline: ASE Transit Bus Study Guide (copyright 2026), Brakes (Test H4), content area D, Wheel Bearings Diagnosis and Repair.
  • The air compressor turns whenever the engine runs. What stops it compressing air once reservoir pressure reaches the maximum setting? Answer: The governor, which holds the unloading valves off their seats. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 34-39, System Components (unloader and governor). Outline: ASE Transit Bus Study Guide (copyright 2026), Brakes (Test H4), content area A, Air Supply and Service Systems Diagnosis and Repair.
  • How large must the combined volume of the service and supply reservoirs of a bus be under FMVSS 121? Answer: At least 12 times the combined volume of all service brake chambers. Source: 49 CFR 571.121 (FMVSS 121, Air brake systems), S5.1.2.1, Reservoirs. Outline: ASE Transit Bus Study Guide (copyright 2026), Brakes (Test H4), content area A, Air Supply and Service Systems Diagnosis and Repair.
  • In the Navy manual's air leakage test, with the engine off and the brakes held fully applied, how much may the gauge pressure drop in 1 minute? Answer: Not more than 3 pounds. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 6, Troubleshooting air brake systems. Outline: ASE Transit Bus Study Guide (copyright 2026), Brakes (Test H4), content area A, Air Supply and Service Systems Diagnosis and Repair.
  • Technician A says the two service brake chambers on one axle must be the same size. Technician B says the two slack adjusters on one axle must have the same effective length. Who is right, under 49 CFR 393.47? Answer: Both technicians. Source: 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation), section 393.47(b) and (c), Brake chambers and slack adjusters. Outline: ASE Transit Bus Study Guide (copyright 2026), Brakes (Test H4), content area B, Mechanical/Foundation Brakes Diagnosis and Repair.
  • Under 49 CFR 393.47, how thin may the lining of an air drum brake on a non-steering axle wear, measured at the shoe center? Answer: To 1/4 inch, or to the wear indicator. Source: 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation), section 393.47(d), Linings and pads. Outline: ASE Transit Bus Study Guide (copyright 2026), Brakes (Test H4), content area B, Mechanical/Foundation Brakes Diagnosis and Repair.
  • Under what conditions is brake chamber pushrod stroke measured, by Appendix A to 49 CFR Part 396? Answer: Engine off, reservoir at 80 to 90 psi, brakes fully applied. Source: 49 CFR Part 396 (Inspection, Repair, and Maintenance), Appendix A, 1.a(5), Readjustment limits. Outline: ASE Transit Bus Study Guide (copyright 2026), Brakes (Test H4), content area B, Mechanical/Foundation Brakes Diagnosis and Repair.
  • What does FMVSS 121 require of the parking brake control of an air-braked bus? Answer: It is separate from the service brake control. Source: 49 CFR 571.121 (FMVSS 121, Air brake systems), S5.6.4, Parking brake control, trucks and buses. Outline: ASE Transit Bus Study Guide (copyright 2026), Brakes (Test H4), content area C, Parking Brakes Diagnosis and Repair.
  • What is the lowest air compressor governor cut-in pressure FMVSS 121 allows for a bus? Answer: 85 psi. Source: 49 CFR 571.121 (FMVSS 121, Air brake systems), S5.1.1.1, Air compressor cut-in pressure. Outline: ASE Transit Bus Study Guide (copyright 2026), Brakes (Test H4), content area A, Air Supply and Service Systems Diagnosis and Repair.

H5 Suspension and steering 8

  • A bus has power steering and a steering wheel 22 inches in diameter. How much lash at the rim does 49 CFR 393.209 allow? Answer: 5 3/4 inches. Source: 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation), section 393.209(b), Steering wheel lash. Outline: ASE Transit Bus Study Guide (copyright 2026), Suspension and Steering (Test H5), content area A, Steering System Diagnosis and Repair.
  • A vehicle seems to travel sideways down a straight road, with the rear wheels not following the front. Which is a cause the Navy manual lists? Answer: Shifted or broken leaf springs. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 12, Steering geometry (tracking). Outline: ASE Transit Bus Study Guide (copyright 2026), Suspension and Steering (Test H5), content area C, Wheel Alignment Diagnosis, Adjustment and Repair.
  • A worn steering shaft universal joint is found to have been built up by welding. What does 49 CFR 393.209 say? Answer: The joint shall not be worn, faulty or repaired by welding. Source: 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation), section 393.209(d), Steering system. Outline: ASE Transit Bus Study Guide (copyright 2026), Suspension and Steering (Test H5), content area A, Steering System Diagnosis and Repair.
  • How much air may an air suspension leak under 49 CFR 393.207, with the air gauge at normal operating pressure? Answer: Not more than 3 psi in 5 minutes. Source: 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation), section 393.207(f), Air suspensions. Outline: ASE Transit Bus Study Guide (copyright 2026), Suspension and Steering (Test H5), content area B, Suspension Systems Diagnosis and Repair.
  • Technician A says a loose axle positioning part is a defect under 49 CFR 393.207. Technician B says a leaf spring that has shifted out of position is a defect under it. Who is right? Answer: Both technicians. Source: 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation), section 393.207(a) and (c), Axles and leaf springs. Outline: ASE Transit Bus Study Guide (copyright 2026), Suspension and Steering (Test H5), content area B, Suspension Systems Diagnosis and Repair.
  • Under 49 CFR 393.207, when may the air pressure regulator valve let air into an air suspension? Answer: Only once at least 55 psi is in the braking system. Source: 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation), section 393.207(f), Air suspensions. Outline: ASE Transit Bus Study Guide (copyright 2026), Suspension and Steering (Test H5), content area B, Suspension Systems Diagnosis and Repair.
  • What does the shackle at the rear of a leaf spring do? Answer: Lets the spring change length as it flexes. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), chapter 30, Leaf springs. Outline: ASE Transit Bus Study Guide (copyright 2026), Suspension and Steering (Test H5), content area B, Suspension Systems Diagnosis and Repair.
  • Which tires may not be on the front wheels of a bus under 49 CFR 393.75? Answer: Regrooved, recapped or retreaded tires. Source: 49 CFR Part 393 (Parts and Accessories Necessary for Safe Operation), section 393.75(d), Tires. Outline: ASE Transit Bus Study Guide (copyright 2026), Suspension and Steering (Test H5), content area D, Wheels and Tires Diagnosis and Repairs.

H6 Electrical and electronic systems 9

  • During a starter control circuit voltage drop test, a high reading is found across the neutral safety switch. What is checked? Answer: The adjustment of the switch. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Solenoid switch circuit resistance test. Outline: ASE Transit Bus Study Guide (copyright 2026), Electrical/Electronic Systems (Test H6), content area B, Battery and Starting System Diagnosis and Repair.
  • How much light must fall on the step tread of a bus stepwell next to the driver when the door is open, under 49 CFR 38.31? Answer: At least 2 foot-candles. Source: 49 CFR Part 38, Subpart B (accessibility specifications for buses, vans and systems), section 38.31, Lighting. Outline: ASE Transit Bus Study Guide (copyright 2026), Electrical/Electronic Systems (Test H6), content area D, Lighting Systems Diagnosis and Repair.
  • In the Navy manual's regulator bypass test, a jumper runs from the battery positive terminal to the alternator field terminal. For how long may the engine be run? Answer: No more than 20 seconds. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Charging circuit diodes bypass procedure. Outline: ASE Transit Bus Study Guide (copyright 2026), Electrical/Electronic Systems (Test H6), content area C, Charging System Diagnosis and Repair.
  • The interior lamps of a bus are wired in parallel. One lamp burns out. What happens to the others? Answer: They keep working. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 11-12, Circuit Configurations (parallel circuits). Outline: ASE Transit Bus Study Guide (copyright 2026), Electrical/Electronic Systems (Test H6), content area A, General Electrical/Electronic System Diagnosis.
  • Lamp bulbs all over a bus burn brighter than normal and keep burning out. Which fault does TM 9-8000 connect with this? Answer: A defective voltage regulator. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 11-11, Ohm's Law. Outline: ASE Transit Bus Study Guide (copyright 2026), Electrical/Electronic Systems (Test H6), content area A, General Electrical/Electronic System Diagnosis.
  • What does the Navy manual check first, before any electrical test on a vehicle? Answer: The battery and its connections. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 4, Troubleshooting lighting systems and electrical accessories. Outline: ASE Transit Bus Study Guide (copyright 2026), Electrical/Electronic Systems (Test H6), content area A, General Electrical/Electronic System Diagnosis.
  • What must the controls of a bus wheelchair lift be interlocked with, under 49 CFR 38.23? Answer: The vehicle brakes, transmission or door. Source: 49 CFR Part 38, Subpart B (accessibility specifications for buses, vans and systems), section 38.23(b)(2), Vehicle lift controls. Outline: ASE Transit Bus Study Guide (copyright 2026), Electrical/Electronic Systems (Test H6), content area E, Related Vehicle Systems Diagnosis and Repair.
  • Which buses must have a public address system under 49 CFR 38.35? Answer: Those over 22 feet long in multiple-stop, fixed-route service. Source: 49 CFR Part 38, Subpart B (accessibility specifications for buses, vans and systems), section 38.35, Public information system. Outline: ASE Transit Bus Study Guide (copyright 2026), Electrical/Electronic Systems (Test H6), content area E, Related Vehicle Systems Diagnosis and Repair.
  • Why does a starting, lighting and ignition (SLI) battery stand up poorly to repeated deep discharge? Answer: Its thin plates limit it to under 100 deep cycles. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 12-6, Deep-Cycle Battery. Outline: ASE Transit Bus Study Guide (copyright 2026), Electrical/Electronic Systems (Test H6), content area B, Battery and Starting System Diagnosis and Repair.

H7 Heating, ventilation and air conditioning 7

  • After one season a system needs more than half a pound of refrigerant. What does the Navy manual conclude? Answer: There is a serious leak that must be found and repaired. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 13, Inspecting the air-conditioning system for leaks. Outline: ASE Transit Bus Study Guide (copyright 2026), Heating, Ventilation, and A/C (Test H7), content area A, A/C System and Component Diagnosis, Service and Repair.
  • Does the definition of "motor vehicle air conditioners" in 40 CFR Part 82, Subpart B, cover the air conditioning of a passenger bus that uses HCFC-22 refrigerant? Answer: No, it leaves those systems out. Source: 40 CFR Part 82, Subpart B (Servicing of Motor Vehicle Air Conditioners), section 82.32(d), Definitions. Outline: ASE Transit Bus Study Guide (copyright 2026), Heating, Ventilation, and A/C (Test H7), content area A, A/C System and Component Diagnosis, Service and Repair.
  • How does the driver control the heat given off by the heater core, by TM 9-8000? Answer: A valve in the heater core feed line controls coolant flow. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), chapter 17, Accessories (heater core). Outline: ASE Transit Bus Study Guide (copyright 2026), Heating, Ventilation, and A/C (Test H7), content area B, Heating and Engine Cooling Systems Diagnosis, Service and Repair.
  • Refrigerant is being added from a can through the low side with the system running. How is the can held? Answer: Upright, so that vapor and not liquid enters the system. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 13, Adding refrigerant to the air-conditioning system. Outline: ASE Transit Bus Study Guide (copyright 2026), Heating, Ventilation, and A/C (Test H7), content area A, A/C System and Component Diagnosis, Service and Repair.
  • Some refrigeration oil comes out with the refrigerant while a system is discharged. What must be done before the system goes back into service? Answer: The lost oil must be replaced. Source: US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992), chapter 13, Purging the air-conditioning system. Outline: ASE Transit Bus Study Guide (copyright 2026), Heating, Ventilation, and A/C (Test H7), content area A, A/C System and Component Diagnosis, Service and Repair.
  • What does a superheat switch inside a compressor do? Answer: Disengages the compressor if it overheats. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 37-7, Compressor. Outline: ASE Transit Bus Study Guide (copyright 2026), Heating, Ventilation, and A/C (Test H7), content area C, HVAC Operating Systems and Related Controls.
  • What engages the drive pulley to the air conditioning compressor when the system is switched on? Answer: The magnetic field of a coil. Source: US Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 37-7, Compressor. Outline: ASE Transit Bus Study Guide (copyright 2026), Heating, Ventilation, and A/C (Test H7), content area C, HVAC Operating Systems and Related Controls.

H8 Preventive maintenance and inspection 10

  • A diesel bus has an exhaust leak that discharges 20 inches forward of the rearmost part of the bus. What does Appendix A to 49 CFR Part 396 say? Answer: The bus does not pass: the limit is 15 inches. Source: 49 CFR Part 396 (Inspection, Repair, and Maintenance), Appendix A, 3, Exhaust System. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area A, Engine Systems.
  • A public transit agency finds a wheelchair lift inoperative, and a spare bus is available. What does 49 CFR 37.163 require? Answer: Take the bus out of service before its next service day. Source: 49 CFR 37.163 (Keeping vehicle lifts in operative condition: public entities), section 37.163(d), Keeping vehicle lifts in operative condition. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area B, Body Interior and Exterior.
  • An air spring has failed and the suspension of a bus is deflated on one axle. How do the periodic inspection standards of Appendix A to 49 CFR Part 396 treat it? Answer: As a suspension defect: the bus does not pass. Source: 49 CFR Part 396 (Inspection, Repair, and Maintenance), Appendix A, 8, Suspension. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area D, Frame and Chassis.
  • An aluminum wheel on the steering axle has been repaired by welding. What do the periodic inspection standards say? Answer: Any welded repair on an aluminum steering axle wheel fails. Source: 49 CFR Part 396 (Inspection, Repair, and Maintenance), Appendix A, 11, Wheels and Rims. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area D, Frame and Chassis.
  • How often must the pushout windows, emergency doors and emergency door marking lights of a bus be inspected under 49 CFR 396.3? Answer: At least every 90 days. Source: 49 CFR Part 396 (Inspection, Repair, and Maintenance), section 396.3(a)(2), Inspection, repair, and maintenance. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area B, Body Interior and Exterior.
  • One windshield wiper of a bus does not work. What do the periodic inspection standards say? Answer: The vehicle does not pass with an inoperative wiper. Source: 49 CFR Part 396 (Inspection, Repair, and Maintenance), Appendix A, 13, Windshield Wipers. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area C, Electrical/Electronic Systems.
  • Technician A says a missing fuel tank filler cap fails the periodic inspection standards. Technician B says a visible fuel leak at any point fails them. Who is right? Answer: Both technicians. Source: 49 CFR Part 396 (Inspection, Repair, and Maintenance), Appendix A, 4, Fuel System. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area A, Engine Systems.
  • Two lengths of air brake hose have been joined by sliding their ends over a piece of tubing and clamping them. What do the periodic inspection standards say? Answer: The splice is a defect and the vehicle does not pass. Source: 49 CFR Part 396 (Inspection, Repair, and Maintenance), Appendix A, 1.d, Brake Hose. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area D, Frame and Chassis.
  • What must the stop request system for mobility aid users do when the control is pressed, under 49 CFR 38.37? Answer: Give both an auditory and a visual indication. Source: 49 CFR Part 38, Subpart B (accessibility specifications for buses, vans and systems), section 38.37, Stop request. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area C, Electrical/Electronic Systems.
  • Which air compressor finding fails the periodic inspection standards of Appendix A to 49 CFR Part 396? Answer: Loose compressor mounting bolts. Source: 49 CFR Part 396 (Inspection, Repair, and Maintenance), Appendix A, 1.h, Air Compressor. Outline: ASE Transit Bus Study Guide (copyright 2026), Preventive Maintenance and Inspection (Test H8), content area A, Engine Systems.

How this list was compiled: Our own questions, written to the test specifications and task lists of tests H1 to H8 in the ASE Transit Bus Study Guide (copyright 2026, https://ase.com/wp-content/uploads/ASE_TransitBus_Study_Guide.pdf, linked from https://ase.com/tests/h1-h8/, both opened 2026-10-08). The eight tests have 50, 50, 40, 50, 45, 50, 40 and 50 scored questions; the bank holds 9, 9, 7, 9, 8, 9, 7 and 10 in that order. Every fact was read on 2026-10-08 in the public text the question names: 49 CFR Parts 393 and 396 (with Appendix A), 49 CFR 571.121, 571.303 and 571.304, 49 CFR Part 38 Subpart B, 49 CFR 37.163 and 40 CFR 82.32 at ecfr.gov; US Army TM 9-8000, Principles of Automotive Vehicles (1985); and US Navy NAVEDTRA 14050, Construction Mechanic, Advanced (1992). 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 transit bus study guide is a practice test: 68 questions of our own on tests H1 to H8. It is unofficial and not affiliated with, endorsed by or sponsored by the National Institute for Automotive Service Excellence (ASE).

Read the full guide

What the H series covers

The eight tests are H1 compressed natural gas engines, H2 diesel engines, H3 drive train, H4 brakes, H5 suspension and steering, H6 electrical, H7 heating and air conditioning, and H8 preventive maintenance and inspection. The bank holds 7 to 10 questions on each.

Where the answers come from

Limits come from federal rules: the air brake, natural gas container and accessibility standards and the commercial vehicle inspection rules. How systems work comes from Army and Navy training manuals, older than current buses.

Timed or on paper

Exam mode asks 50 mixed questions in 75 minutes, the scored count and time of H1, H2, H4 and H8. This ASE H series practice test also prints on paper.

  • Federal Parts 393 and 396 exempt transit run by a state or city. They are cited as a public yardstick; your agency's maintenance plan governs.

Questions and answers

Is there an official transit bus ASE study guide?

Yes. ASE publishes a free Transit Bus Study Guide with the test specifications, task lists and sample questions for tests H1 to H8. This page is a separate, unofficial practice test built on its outline, and it uses none of its sample questions.

How many questions are on the ASE transit bus tests?

By ASE's 2026 study guide, H1, H2, H4, H6 and H8 have 60 questions, H5 has 55, and H3 and H7 have 50. Ten on each are unscored research questions. The table above gives each time limit.

Which tests make a Master Transit Bus Technician?

ASE's page says technicians certified in H1 or H2, plus H3 to H8, are recognized as ASE-Certified Master Transit Bus Technicians. Each certification is kept by retesting every five years.

How do the ASE transit bus tests differ from the truck tests?

ASE's page says several H tests parallel the medium-heavy truck and school bus tests, but each covers systems specific to transit buses. Here that means natural gas fuel containers, wheelchair lifts, stepwell lighting and emergency exits.

Does ASE H7 certification count as EPA 609 certification?

No. ASE's study guide notes that its HVAC certifications, H7 among them, do not satisfy EPA's Section 609 requirement for refrigerant handling. That takes a separate approved program.

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