Sample Questions
Free Sample Exam Questions
Here are a few sample questions directly from our complete 130-question bank:
Sample Question 1
When the diesel engine is running, what is the primary function of the air compressor?
- Takes in atmospheric air and compresses it into the supply reservoirs ✓
- Draws air back out of the reservoirs and sends it through the air dryer to remove moisture
- Compresses brake fluid so that it can be delivered to the wheel cylinders
- Creates a vacuum that boosts the force applied at the brake pedal
Explanation: The compressor takes air from the atmosphere, compresses it and pumps it to the supply reservoir for as long as the engine runs. The governor stops the pumping at cut-out pressure (usually between 105 and 135 psi).
Sample Question 2
According to the ICBC guide, within what range does the governor's maximum (cut-out) pressure fall on different vehicles?
- Between 105 and 135 psi (724–931 kPa) ✓
- Between 145 and 160 psi (1,000–1,103 kPa)
- Between 80 and 95 psi (552–655 kPa)
- Between 150 and 165 psi (1,034–1,138 kPa)
Explanation: ICBC Driving Commercial Vehicles (Governor): the maximum pressure on different vehicles varies between 105 and 135 psi (about 125 psi is typical), the governor restarts the compressor about 20 psi lower, and it must restart it before pressure falls below 80 to 85 psi. The BC inspection manual gives narrower limits for rejecting a vehicle in service (cut-in below 100 psi, cut-out below 120 psi or above 145 psi). Those limits decide whether one particular vehicle is rejected; they are not the range the guide teaches. The safety valve (about 150 psi) is a separate back-up.
Sample Question 3
If the governor fails to unload the compressor, what does the safety valve on the first reservoir do?
- Vents air to the atmosphere at about 150 psi to protect the reservoirs from over-pressure ✓
- Closes the compressor intake at about 120 psi so that the governor can restart the pump
- Passes air from the primary reservoir into the secondary reservoir when cut-out is reached
- Opens the air dryer purge valve at about 100 psi to expel the collected moisture
Explanation: The safety valve protects tanks from rupture if the governor fails by venting air at approximately 150 psi (1,034 kPa).
Sample Question 4
During the daily commercial vehicle pre-trip inspection, why must air supply reservoirs be manually drained?
- Removes the water and oil that collect in the tanks and would gum up valves or freeze ✓
- Relieves residual pressure so that the spring brakes cannot apply while the vehicle is parked overnight
- Resets the governor so that its cut-in and cut-out settings are correct for the next trip
- Empties the supply tank so the one-way check valves can refill both service reservoirs evenly
Explanation: Water and oil from the compressor condense in the cold tanks and form sludge. Draining the tanks daily (the wet tank first) keeps this sludge out of the air valves and prevents corrosion and freeze-up.
Sample Question 5
At what pressure must the low air warning device (light and buzzer) come on?
- Before either circuit falls below 60 psi (414 kPa) ✓
- Once either circuit drops below 100 psi (690 kPa), the minimum cut-in pressure
- At 30 psi (207 kPa), before the spring brakes start to apply
- At 85 psi (586 kPa), when the compressor cuts in
Explanation: ICBC: the low-air warning device (light and buzzer) must come on when air pressure drops below 60 psi (414 kPa). The BC inspection manual rejects a warning device that does not operate below 60 psi and puts the vehicle out of service if it does not operate below 55 psi.
Frequently Asked Questions
Exam FAQs
Is this ICBC air brake practice test free?
Yes — 100% free with unlimited test and practice attempts for the BC Code 15 endorsement.
How many questions are on the real ICBC air brake knowledge test?
The real ICBC test has 25 multiple-choice questions. You need 20 correct answers (80%) to pass.
At what pressure must the low air warning activate in BC?
The low air warning light and buzzer must come on before pressure in either circuit falls below 60 psi (414 kPa). In BC, a vehicle is out of service if the warning does not operate below 55 psi (380 kPa).
At what pressure are air brake governors usually set to unload the compressor?
The ICBC guide says the maximum pressure varies between 105 and 135 psi (724–931 kPa) depending on the vehicle, with about 20 psi between cut-out and cut-in. The BC inspection manual uses separate limits for rejecting a vehicle in service: cut-in below 100 psi, or cut-out below 120 psi or above 145 psi.
What is the maximum allowable air leakage rate for a single vehicle?
Air loss must not exceed 3 psi per minute with the engine off and service brakes fully applied.