BRAKES

When performing a hydro-boost brake booster function test the brake pedal should be depressed several times to discharge the accumulator. When the engine is started, with your foot on the brake pedal, the pedal should:

sink slightly toward the floor, then push back against your foot.

The purpose of the charcoal filter in the vacuum hose between the engine and the vacuum brake booster is to:

trap gasoline vapors to keep them from entering the booster

The proper operation of a vacuum brake booster requires that the engine be capable of supplying at least:

15 in. Hg vacuum

Modern antilock brake systems typically hold tire slip on dry pavement to between:

5 and 20 percent

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

Allows drivers to drive more closely to the vehicle in front

A hydraulically operated booster unit stores fluid under pressure by means of:

An accumulator

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

Both

Technician A says that to check the operation of a vacuum brake booster, the brake pedal should be depressed until the assist is depleted and then start the engine. Technician B says that the brake pedal should drop when the engine starts, if the booster is okay. Which technician is correct?

Both

Two technicians are discussing vacuum suspended brake boosters. Technician A says that when the engine is running and the driver's foot is off the brake pedal, a vacuum is present on both sides of the booster diaphragm. Technician B says that when the brakes are in the applied position, engine vacuum is present on the front side of the diaphragm. Which technician is correct?

Both

What causes the ABS control module to switch from a "stand-by" mode to an active mode?

Brake pedal switch

What precaution should be taken before servicing an ABS that uses a high pressure accumulator?

Discharge the accumulator

A vacuum is described as any pressure that is higher than atmospheric pressure.

False

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

Frequency

A defective vacuum brake booster will cause a:

Hard brake pedal

The three phases of ABS operation are pressure:

Hold, release, increase

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

Hydraulic modulator unit

Technician A states a magnetic-inductive WSS is an active speed sensor. Technician B states a magnetic-inductive WSS produces DC voltage. Which technician is correct?

Niether

To provide the driver with a sense of "feel" during braking, vacuum boosters use a:

Reaction disk

When blowing through the vacuum supply hose, if air passes through the check valve into the booster:

Replace the check valve

A digital wheel speed sensor produces a(an) ________ type of signal.

Square wave

Technician A says even though the driver is turning the steering wheel, the vehicle will continue in a straight line if the front wheels are locked. Technician B says the ABS system operates at a higher pressure than the driver does with his/her foot. Who is right?

Tech A only

Technician A says power brakes were developed because of increased vehicle weight and increased speed capabilities. Technician B says disc brakes systems all operate with power assist. Which technician is correct?

Tech A only

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

Tech A only

Two technicians are discussing vacuum brake boosters. Technician A says that a low, soft brake pedal is an indication of a defective booster. Technician B says that there should be at least two power-assisted brake applications after the engine stops running. Which technician is correct?

Tech A only

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?

Tech B only

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?

Tech B only

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

Tech B only

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 can produce shorter stops than an antilock system. Which technician is correct?

Technician B only

What is the function of the ABS solenoids?

They open and close hydraulic passageways

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

Two-channel ABS