Ontario AZ Licence Practice Test 2026: Practice test 6

Practice test 6 of 6 for the Ontario AZ Licence Practice Test: 20 more questions with answers and explanations.

Commercial vehicle
Ontario
150 questions
Checked October 10, 2026

Question 1 of 20
What does the governor do?
- It removes water and oil from the air
- It measures push rod stroke at each wheel
- It controls when the compressor cuts in and cuts out
- It stops the truck if you go over the speed limit
Show answer
Answer: C. It controls when the compressor cuts in and cuts out
The governor tells the compressor when to start (cut in) and stop (cut out) pumping air into the system.
Question 2 of 20
Since September 1, 2023, what do Class A or D drivers with a Z endorsement complete before renewing their licence?
- An air brake knowledge test at a DriveTest centre
- A full road test in an air-brake vehicle
- A new full air brake course with a fleet owner
- An online Air Brakes Refresher Training module
Show answer
Answer: D. An online Air Brakes Refresher Training module
The online refresher module replaced the air brake knowledge test at renewal.
Question 3 of 20
If you double your speed, what happens to the stopping distance?
- It becomes four times as long
- It becomes eight times as long
- It doubles
- It stays the same
Show answer
Answer: A. It becomes four times as long
Doubling speed increases stopping distance four times.
Question 4 of 20
When measuring applied push rod stroke, what pressure should the gauges show?
- 380 to 414 kPa (55 to 60 psi)
- 621 to 690 kPa (90 to 100 psi)
- 1000 to 1035 kPa (145 to 150 psi)
- 138 to 173 kPa (20 to 25 psi)
Show answer
Answer: B. 621 to 690 kPa (90 to 100 psi)
Keep pressure at 621 to 690 kPa (90 to 100 psi) during the adjustment check, with the service brakes fully applied.
Question 5 of 20
If you double the weight of your vehicle, what happens to the stopping distance?
- It doubles
- It halves
- It stays the same
- It increases eight times
Show answer
Answer: A. It doubles
Doubling the weight doubles the stopping distance.
Question 6 of 20
About how much air pressure is needed to fully release (hold off) spring brakes?
- 69 kPa (10 psi)
- 207 kPa (30 psi)
- 1000 kPa (145 psi)
- 414 kPa (60 psi)
Show answer
Answer: D. 414 kPa (60 psi)
Spring brakes need about 414 kPa (60 psi) to be fully released. Below that, the springs start to apply the brakes.
Question 7 of 20
What does the trailer supply valve control knob usually look like?
- A yellow, diamond-shaped knob
- A red, eight-sided push-pull knob
- A blue, round knob
- A green toggle switch
Show answer
Answer: B. A red, eight-sided push-pull knob
The trailer supply valve has a red, eight-sided push-pull knob.
Question 8 of 20
You hold a Class D licence and want a Z endorsement. Who must give your air brake course?
- A private instructor with no approval
- Any online provider
- A community college only
- A vehicle fleet owner
Show answer
Answer: D. A vehicle fleet owner
Holders of B, C, D, E, F or G licences must take the course through a fleet owner. Class A holders upgrading may use any of the three provider types.
Question 9 of 20
In a dual air brake system, what happens if one circuit fails?
- All the brakes release at once and cannot be applied
- The trailer uncouples automatically from the tractor
- The other circuit should still be able to stop the vehicle
- The engine shuts off and the vehicle coasts to a stop
Show answer
Answer: C. The other circuit should still be able to stop the vehicle
Dual systems split air into primary and secondary circuits so one can still stop the vehicle if the other fails.
Question 10 of 20
Where should you do the mechanical part of the air brake inspection?
- In a live traffic lane with your four-way flashers on
- On a hill, so the brakes are under load while you check them
- Anywhere, with the engine running at high rpm
- On level ground, away from traffic, with the engine off and wheels chocked
Show answer
Answer: D. On level ground, away from traffic, with the engine off and wheels chocked
Park on level ground away from traffic, shut off the engine, apply the spring brakes and chock the wheels.
Question 11 of 20
What is a DD3 chamber?
- A spring brake chamber with a caging bolt, used only on trailers
- A bus and coach brake chamber with three air connections and no large spring
- A diesel fuel filter used on buses and motor coaches
- A double-diaphragm gauge that shows two pressures at once
Show answer
Answer: B. A bus and coach brake chamber with three air connections and no large spring
DD3 chambers are used on buses and coaches. They have three air connections and no large power spring.
Question 12 of 20
What is a wig wag?
- A gauge that measures push rod stroke at each wheel
- A warning arm that drops into view when air pressure is low
- A valve under each air tank that drains water and oil
- A type of automatic slack adjuster used on trailers
Show answer
Answer: B. A warning arm that drops into view when air pressure is low
A wig wag drops into the driver's view when system pressure falls too low.
Question 13 of 20
Before testing the low air warning, the system should have at least what pressure?
- 1000 kPa (145 psi)
- 207 kPa (30 psi)
- 621 kPa (90 psi)
- 414 kPa (60 psi)
Show answer
Answer: C. 621 kPa (90 psi)
Build pressure to at least 621 kPa (90 psi), turn the ignition on, then press and release the brake pedal until the warning comes on.
Question 14 of 20
What is brake fade?
- The low air warning slowly fading out
- Paint wearing off the brake drums over time
- Overheated brakes losing power, so you must push harder
- A slow leak in one of the air tanks
Show answer
Answer: C. Overheated brakes losing power, so you must push harder
As brake parts overheat, they work less well and you must push harder on the pedal.
Question 15 of 20
When you close the trailer supply valve during the test, what should the trailer spring brakes do?
- Release
- Stay as they were
- Apply
- Lock the tractor's steering
Show answer
Answer: C. Apply
Trailer spring brakes must apply when the trailer supply valve is closed. If they do not, the system is defective.
Question 16 of 20
About how long is the delay between pressing the brake pedal and the air brakes applying?
- There is no delay with air brakes
- About 10 seconds
- Up to about half a second
- About 5 seconds
Show answer
Answer: C. Up to about half a second
Air takes time to travel through the lines, so there is a split-second delay of up to about one-half second.
Question 17 of 20
In the air-loss test, what is the most pressure a tractor with two or more trailers may lose in one minute?
- 69 kPa (10 psi)
- 21 kPa (3 psi)
- 28 kPa (4 psi)
- 41 kPa (6 psi)
Show answer
Answer: D. 41 kPa (6 psi)
A tractor with two or more trailers may lose no more than 41 kPa (6 psi) per minute.
Question 18 of 20
What is the usual difference between the governor's cut-out and cut-in pressures?
- 345 to 414 kPa (50 to 60 psi)
- 138 to 173 kPa (20 to 25 psi)
- 690 kPa (100 psi)
- 7 to 14 kPa (1 to 2 psi)
Show answer
Answer: B. 138 to 173 kPa (20 to 25 psi)
The cut-in pressure is usually 138 to 173 kPa (20 to 25 psi) below the cut-out pressure.
Question 19 of 20
What is the typical normal operating range of an air brake system?
- 380 to 414 kPa (55 to 60 psi)
- 690 to 828 kPa (100 to 120 psi)
- 1035 to 1200 kPa (150 to 175 psi)
- 138 to 311 kPa (20 to 45 psi)
Show answer
Answer: B. 690 to 828 kPa (100 to 120 psi)
Most systems run between 690 and 828 kPa (100 to 120 psi).
Question 20 of 20
In a dual air system, where does air go after the supply (wet) tank?
- Into the fuel tank to help push the fuel
- Straight to the exhaust, then out of the vehicle
- Into the primary and secondary (dry) tanks
- Back into the compressor to be pumped again
Show answer
Answer: C. Into the primary and secondary (dry) tanks
Air from the supply tank is split into the primary and secondary dual-service tanks.

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