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Questions and Answers
What is a primary disadvantage of anti-lock brakes?
What is a primary disadvantage of anti-lock brakes?
What can cause inconsistent stopping distances with anti-lock brakes?
What can cause inconsistent stopping distances with anti-lock brakes?
What typically alerts the driver to a malfunction in the ABS system?
What typically alerts the driver to a malfunction in the ABS system?
What is a common source of ABS problems?
What is a common source of ABS problems?
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Why is the maintenance of anti-lock brake systems required?
Why is the maintenance of anti-lock brake systems required?
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What might indicate a fault in an ABS system?
What might indicate a fault in an ABS system?
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What should be checked first when diagnosing ABS issues?
What should be checked first when diagnosing ABS issues?
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What is a possible consequence of contaminated brake fluid in an ABS system?
What is a possible consequence of contaminated brake fluid in an ABS system?
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What is the primary benefit of traction control when accelerating from a stop or on slippery hills?
What is the primary benefit of traction control when accelerating from a stop or on slippery hills?
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When should traction control be turned off?
When should traction control be turned off?
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What might you notice when traction control is turned off?
What might you notice when traction control is turned off?
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What is the primary role of an automatic tire chain system?
What is the primary role of an automatic tire chain system?
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In which condition is traction control least effective?
In which condition is traction control least effective?
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What should a driver do when driving in slippery conditions?
What should a driver do when driving in slippery conditions?
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How does traction control engage?
How does traction control engage?
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What happens to a vehicle's handling when traction control is active?
What happens to a vehicle's handling when traction control is active?
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What is the primary function of the wheel speed sensors in an ABS system?
What is the primary function of the wheel speed sensors in an ABS system?
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How often does the ABS actuator cycle pressure to the brake assemblies to prevent wheel lockup?
How often does the ABS actuator cycle pressure to the brake assemblies to prevent wheel lockup?
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What role does the ABS control module play in the anti-lock braking system?
What role does the ABS control module play in the anti-lock braking system?
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Which of the following components is responsible for storing brake fluid under high pressure in an ABS system?
Which of the following components is responsible for storing brake fluid under high pressure in an ABS system?
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What does a decrease in a wheel speed sensor’s signal frequency indicate?
What does a decrease in a wheel speed sensor’s signal frequency indicate?
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What happens when the ABS warning light illuminates on the dashboard?
What happens when the ABS warning light illuminates on the dashboard?
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What is the function of the solenoid valve block in the ABS system?
What is the function of the solenoid valve block in the ABS system?
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Which component directly compares signals from each of the wheel sensors to manage braking?
Which component directly compares signals from each of the wheel sensors to manage braking?
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What is the primary function of the isolation mode in the ABS system?
What is the primary function of the isolation mode in the ABS system?
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In dump mode, what happens if the wheel is still decelerating too rapidly?
In dump mode, what happens if the wheel is still decelerating too rapidly?
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What is the amperage range for the modulator solenoid in isolation mode?
What is the amperage range for the modulator solenoid in isolation mode?
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What indicator prompts the ECU to stop sending current to the hydraulic unit in the reapply mode?
What indicator prompts the ECU to stop sending current to the hydraulic unit in the reapply mode?
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What does a lingering or flickering traction control system (TCS) light indicate?
What does a lingering or flickering traction control system (TCS) light indicate?
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How does the four-wheel, four-channel ABS system differ from the three-channel system?
How does the four-wheel, four-channel ABS system differ from the three-channel system?
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What role does the solenoid play during the dumping mode when the tire continues to slip?
What role does the solenoid play during the dumping mode when the tire continues to slip?
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What can potentially cause the TCS computer to fail?
What can potentially cause the TCS computer to fail?
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What occurs when the control module detects that the tire speed has increased in the reapply mode?
What occurs when the control module detects that the tire speed has increased in the reapply mode?
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When is it safe to drive with the TCS light on?
When is it safe to drive with the TCS light on?
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How does traction control primarily function?
How does traction control primarily function?
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What is the function of the outlet valve during dump mode?
What is the function of the outlet valve during dump mode?
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What could be a consequence of driving with a non-functional TCS?
What could be a consequence of driving with a non-functional TCS?
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Why is it essential to maintain your TCS in working condition?
Why is it essential to maintain your TCS in working condition?
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What is a primary component involved in the functioning of traction control?
What is a primary component involved in the functioning of traction control?
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What action is recommended if the TCS light remains on during driving?
What action is recommended if the TCS light remains on during driving?
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What does brake-by-wire technology replace in traditional braking systems?
What does brake-by-wire technology replace in traditional braking systems?
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What is one of the main benefits of implementing brake-by-wire systems?
What is one of the main benefits of implementing brake-by-wire systems?
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Which component is NOT typically included in a vehicle's brake-by-wire system?
Which component is NOT typically included in a vehicle's brake-by-wire system?
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What is a suggested solution to enhance safety in brake-by-wire systems?
What is a suggested solution to enhance safety in brake-by-wire systems?
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What type of motors are most frequently used to power actuators in brake-by-wire systems?
What type of motors are most frequently used to power actuators in brake-by-wire systems?
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Which communication network is often used in brake-by-wire systems to relay instructions?
Which communication network is often used in brake-by-wire systems to relay instructions?
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What is the primary role of the electronic control units in a brake-by-wire system?
What is the primary role of the electronic control units in a brake-by-wire system?
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What must be addressed to encourage widespread adoption of brake-by-wire systems?
What must be addressed to encourage widespread adoption of brake-by-wire systems?
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Study Notes
Anti-lock Braking System (ABS)
- ABS is a system designed to prevent brake lockup
- Applying too much pressure to the brakes, causing the axle and wheels to stop turning completely
- When wheels stop turning but the vehicle is still moving, skidding occurs, leading to loss of control, which can be dangerous at high speeds.
- ABS is designed to prevent brakes from locking up and skidding when braking hard or when braking on wet or slippery surfaces.
- ABS may increase stopping distance on dry surfaces, but on wet or slick surfaces, it may reduce stopping distance by up to 25% or more, sometimes making the difference between a safe stop and an accident.
- It helps to control wheel lockups during hard braking
- A tire that is on the verge of slipping (10% to 20%) produces more friction than a locked and skidding tire (100% slippage)
- The only exception to this when a tire is on loose snow. A wedge of snow will build up ahead of the locked tire. This allows it to stop in a shorter distance than a rolling tire. This is why some vehicles have an on/off switch to deactivate the antilock system when driving on snow.
Electronic Brake System
- Anti-lock braking systems (ABS)
- Traction and stability control systems
- ABS service
- Traction and stability control system service
- Final system check
- An electronic control unit (ECU) controls braking fluid reservoir, pump and motor assembly, sensor wiring, master cylinder, brake pedal, wheel speed sensor, brake pressure modulator, and disc brake accumulator and braking circuit
Components of ABS
- Wheel speed sensors
- ABS actuator
- ABS control module
- ABS warning light
Signal Production
- Wheel speed sensors produce alternating current (AC) signals that correspond to wheel and tire speed.
- These signals are fed to the anti-lock brake system control module.
- As the tire rotates, the moving teeth on the sensor rotor induce current in the sensor winding.
Signal Frequency and Modulation
- A rapid decrease in a sensor's signal frequency indicates that a tire is losing traction and locking up.
- The control module then sends an electrical signal to the hydraulic modulator to pulsate hydraulic pressure to the affected wheel brake, modulating braking effort.
Brake Function and Resistance
- Brakes slow or stop a vehicle by utilizing two types of resistance: resistance at the brake and resistance between the road and tire.
- When resistance at the brake is less than resistance between the road and tire (within 10% - 30% of slip ratio), braking can be controlled stably.
- When the resistance at the brake is greater than resistance between the road and tire, the tires lock up, slip, and the vehicle begins skidding.
- Moving vehicles possess Kinetic Energy.
- Brakes convert the kinetic energy into heat by rubbing a disk or brake shoe (in disc brake) or a brake shoe against a brake drum (in a drum brake).
- Maximum deceleration is achieved when maximum energy conversion takes place in the braking system.
- This conversion (energy to heat) is less efficient when a tire is skidding.
Skidding
- When the tires skid:
- Braking distance increases
- Steering control is lost
- Tire wear will be abnormal.
- During a skid, stopping distance increases because the adhesion between the skidding wheel and the road is less compared to a wheel on the verge of skidding
- This is achieved using the Anti-Lock Braking System (ABS)
ABS operation
- ABS works in a closed loop that has several inputs and outputs.
- Inputs primarily come from the wheel speed sensors
- The ECU (electronic control unit) is the main output that controls brake system pressure.
- It compares the signals from each wheel sensor to calculate acceleration or deceleration of an individual wheel.
- The ABS action is to regulate (modulate) fluid pressure sent to each wheel brake assembly during ABS operation. This regulation occurs up to around 15 to 20 times per second, preventing wheel lockup. (pressure modulation)
Modulator Components
- Fluid reservoir and pump: Holds an extra supply of brake fluid to reduce pressure.
- Solenoid valve block: Computer-controlled valves that control brake fluid flow to the wheel brakes
- Master cylinder-booster assembly: Conventional master cylinder and booster for normal braking
ABS Indicator Light
- An ABS indicator light on the dashboard signifies a problem in the system that requires checking
- Typical malfunctions include a failing ABS module, low fluid levels, broken wheel speed sensors, or the system is turned off.
- The ABS module shares components with the traction control system
Traction Control System (TCS)
- TCS is a system that helps a vehicle maintain traction to prevent wheels from spinning and losing traction on slippery or dangerous road conditions (ice, snow or rain).
- TCS automatically senses when a wheel loses traction
- During loss of traction, it shifts power from the wheel that is slipping to the wheels that are firmly gripping the pavement.
Additional Notes
- For maximum braking and control, tire slip must be avoided. When tires slip, friction with the road surface drops, increasing stopping distances. ABS modulates braking effort at controlled wheels to reduce stopping distance, improving directional stability.
- A vehicle's ABS module notifies the driver of malfunctions with the warning light. Faulty wheel sensors, broken or disconnected wiring, and problems with the sensor wiring are the most common causes to the system problems.
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Description
Test your knowledge on the fundamentals of anti-lock braking systems (ABS). This quiz covers the common malfunctions, maintenance requirements, and diagnoses associated with ABS. Understanding these elements is crucial for automotive safety and performance.
