Question 1

Technician A says that the ABS system may not result in shorter stopping distance compared to brakes without ABS. Technician B says that a pulsating brake pedal during normal braking is a characteristic feature of most ABS-equipped vehicles. Which technician is correct?

Accepted Answer

Technician A is correct because ABS is designed to prevent wheel lockup, not necessarily to shorten stopping distances. Technician B is correct because a pulsating brake pedal is a normal characteristic of ABS operation during braking.

Question 2

The maximum traction between a tire and the road occurs when the tire is ________.

Accepted Answer

The maximum traction between a tire and the road occurs when the tire is slipping 10% to 20%. This is because a controlled amount of slip allows the tire to maintain better contact and grip with the road surface, optimizing traction.

Question 3

Technician A says that ABS-equipped vehicles can stop quickly and without skidding on all road surfaces even if covered with ice. Technician B says that steering is possible during an ABS stop. Which technician is correct?

Accepted Answer

Technician B is correct because ABS allows for steering control during a braking event by preventing the wheels from locking up, but it does not guarantee shorter stopping distances on all surfaces, especially on ice, as implied by Technician A.

Question 4

A customer wanted the ABS checked because of tire chirp noise during hard braking. Technician A says that the speed sensors may be defective. Technician B says that tire chirp is normal during an ABS stop on dry pavement. Which technician is correct?

Accepted Answer

Tire chirp can be normal during an ABS stop on dry pavement as it indicates the ABS system is rapidly pulsing the brakes to prevent wheel lockup, which can cause a chirping sound. This does not necessarily indicate a defect with the speed sensors.

Question 5

Two technicians are discussing ABS wheel speed sensors. Technician A says that some ABS systems use a sensor located in the rear-axle pinion gear area. Technician B says that all ABS systems use a wheel speed sensor at each wheel. Which technician is correct?

Accepted Answer

Technician A is correct because some ABS systems, particularly on older or certain types of vehicles, use a sensor located in the rear-axle pinion gear area to monitor wheel speed indirectly. Technician B is incorrect because not all ABS systems use a wheel speed sensor at each wheel; some systems use alternative methods for monitoring wheel speed.

Question 6

Technician A says that most ABS units are non-integral.. Technician B says that the ABS is disabled (does not function) below about 5 mph (8 km/h). Which technician is correct?

Accepted Answer

Both statements are correct. Most ABS units are indeed non-integral, meaning they are separate from the main hydraulic braking system, and ABS systems are typically designed to disable below certain speeds (around 5 mph or 8 km/h) because at very low speeds, the system's ability to prevent wheel lockup is less critical and can sometimes interfere with normal braking.

Question 7

Which type of antilock braking system (ABS) requires the use of four wheel speed sensors?

Accepted Answer

Four channel ABS systems require the use of four wheel speed sensors, one for each wheel, to monitor and control the braking force independently at each wheel. This allows for the most precise control over skidding and stopping distances.

Question 8

Technician A says that ABS brakes are designed to allow the front wheel to be steered during heavy braking. Technician B says that the ABS dash warning lamp is amber. Which technician is correct?

Accepted Answer

ABS (Anti-lock Braking System) is designed to prevent the wheels from locking up during heavy braking, allowing the driver to maintain steering control, which aligns with Technician A's statement. The ABS warning light on the dashboard is indeed amber (or yellow), confirming Technician B's statement as well.

Question 9

The faster a wheel rotates, the higher the frequency produced by a wheel speed sensor.

Accepted Answer

The frequency produced by a wheel speed sensor increases with the rotation speed of the wheel because the sensor generates more pulses per unit of time as the wheel spins faster.

Question 10

Technician A says that some wheel speed sensors are enclosed in a wheel bearing assembly. Technician B says that some wheel speed sensors are exposed to possible damage from road debris. Which technician is correct?

Accepted Answer

Both statements are correct. Some wheel speed sensors are indeed integrated into the wheel bearing assembly, protecting them from external elements, while others are mounted externally where they can be exposed to potential damage from road debris.

Question 11

Before servicing the brakes in a typical integral ABS, the technician should pump the brake pedal ________.

Accepted Answer

Before servicing the brakes in a typical integral ABS, the technician should pump the brake pedal 25 times or more. This is to ensure that the high-pressure accumulator is fully discharged, preventing any unexpected application of the brakes or injury while working on the system. Integral ABS systems often store a significant amount of pressure, and failure to properly discharge this pressure can be dangerous.

Question 12

Magnetic wheel speed sensors are being discussed. Technician A says that the wheel speed sensors are magnetic. Technician B says that the toothed sensor ring is magnetic. Which technician is correct?

Accepted Answer

Technician A is correct because magnetic wheel speed sensors use a magnetic field to detect wheel speed, while the toothed sensor ring, also known as a tone wheel, is typically made of metal and is not magnetic itself; it serves as a target for the magnetic sensor.

Question 13

Which of the following components is common to all vehicles equipped with ABS?

Accepted Answer

The Hydraulic Control Unit (HCU) is a common component in all vehicles equipped with Anti-lock Braking Systems (ABS). It controls the pressure to the brakes during ABS operation.

Question 14

The ABS computer uses the ________ signal from a wheel speed sensor.

Accepted Answer

The ABS computer uses the frequency signal from a wheel speed sensor to determine the speed of the wheel.

Question 15

Which of the following is NOT a function of an antilock brake system (ABS)?

Accepted Answer

ABS is designed to help maintain control and stability of the vehicle during emergency braking, not to enable drivers to follow other vehicles more closely.

Question 16

Technician A says an antilock system that operates on the select-low principle will control each rear wheel individually. Technician B says systems using the select-low principle regulates rear wheel brake pressure to both rear wheel simultaneously. Which technician is correct?

Accepted Answer

Technician B is correct because the select-low principle in antilock brake systems (ABS) applies brake pressure to both rear wheels simultaneously, based on the wheel with the least traction. This ensures stability and prevents skidding during braking.

Question 17

Technician A says an antilock brake system will always produce the shortest possible stops. Technician B says when braking on loose gravel or dirt, a system that can lock the wheels produces shorter stops than an antilock system. Which technician is correct?

Accepted Answer

Technician B is correct because on loose gravel or dirt, a locked wheel can create a wedge of material in front of the tire, which can lead to shorter stopping distances compared to an antilock brake system (ABS) that prevents wheel lock-up. ABS is designed to maintain control during braking, not necessarily to minimize stopping distance under all conditions.

Question 18

Which antilock component creates current frequencies that change with wheel rotational speed?

Accepted Answer

Wheel speed sensors are responsible for monitoring the rotational speed of each wheel and sending this information to the antilock braking system's (ABS) electronic control unit. The current frequencies generated by these sensors change with the wheel's rotational speed, allowing the system to detect when a wheel is about to lock up during braking.

Question 19

Technician A says digital wheel speed sensors produce a variable frequency AC voltage. Technician B says digital wheel speed sensors use a DC reference voltage supply and produce a square wave signal. Which technician is correct?

Accepted Answer

Technician B is correct because digital wheel speed sensors indeed use a DC reference voltage and produce a square wave signal, unlike analog sensors that generate a variable frequency AC voltage as described by Technician A.

Question 20

A technician is trying to identify which type of antilock system is installed on a vehicle. A speed sensor is attached to the rear differential housing. Which type of system could this be?

Accepted Answer

A three-channel ABS system typically has one speed sensor on each front wheel and one on the rear differential, which matches the description given.

Quiz 106: Abs Components and Operation