Automobile & Light Truck Certification Test A5 Brakes flashcards

A diagnostic test for vacuum brake boosters where the pedal is held down with the engine off, then the engine is started. A functional booster will cause the pedal to drop slightly.

• Checks for proper vacuum assistance.
• Pedal should drop when engine starts.
• No drop indicates booster or vacuum issue.

Memory trick: Hard pedal, no drop, booster's a flop.

DOT 4 and DOT 5.1 brake fluids are both glycol-ether based and are fully compatible with each other and with systems designed for DOT 3, 4, or 5.1.

• DOT 3, DOT 4, and DOT 5.1 are glycol-ether based.
• These fluids are hygroscopic and compatible with each other.
• DOT 5 is silicone-based and NOT compatible with other DOT fluids.
• Higher DOT numbers (4, 5.1) generally indicate higher boiling points.

Memory trick: Glycol fluids mix, but silicone stands alone.

A malfunction of the electric pump motor within the ABS Hydraulic Control Unit, which is responsible for maintaining and modulating brake fluid pressure during ABS events.

• Causes issues specifically during ABS activation
• Can result in a hard pedal or poor ABS performance
• Often accompanied by ABS warning light

Memory trick: ABS pedal's hard, pump motor's tired, pressure control is now misfired!

Over time, brake fluid's additives (especially corrosion inhibitors) degrade, and it absorbs moisture. This combination leads to internal corrosion of metal hydraulic components (like the master cylinder bore and caliper pistons) and breakdown of rubber seals, resulting in dark, sludgy, and contaminated fluid.

• Fluid additives degrade.
• Moisture absorption.
• Causes internal corrosion.
• Breaks down rubber seals.

Memory trick: Dark fluid, like a muddy bog, means internal rust and components log!

A ruptured brake booster diaphragm prevents the booster from holding vacuum and creating the necessary pressure differential to assist braking, resulting in a 'hard' brake pedal.

• Brake boosters use engine vacuum to assist braking.
• The diaphragm separates atmospheric pressure from vacuum.
• A rupture allows vacuum to escape, neutralizing the assist.
• Symptom: hard brake pedal requiring excessive force.

Memory trick: Hard pedal + no vacuum hold = a 'hole' in the booster.

A safety valve that monitors pressure balance between the primary and secondary brake circuits and illuminates a warning light if a significant pressure difference is detected.

• Indicates a hydraulic pressure loss in one circuit.
• Does not stop the leak, only warns the driver.
• Often integrated into a combination valve.

Memory trick: Warning light: Low fluid, parking brake, or pressure imbalance.

A blockage or collapse within a brake line, preventing the proper flow of hydraulic fluid to the brake component it serves.

• Can be caused by corrosion or internal damage
• Prevents fluid from reaching caliper/wheel cylinder
• Leads to lack of braking at affected wheel or difficulty bleeding

Memory trick: Firm pedal, no fluid's flow, restricted line is the pathway's woe!

To diagnose an internally collapsed flexible brake hose causing delayed brake release, clamp the suspect hose with vice grips (or a specialized brake line clamp). Depress the brake pedal. If the pedal becomes significantly firmer than before, it suggests the hose was the culprit, as the clamp is mimicking its internal restriction and preventing fluid return.

• Causes delayed brake release.
• Acts as a one-way valve.
• Clamping restricts fluid.
• Pedal feels firmer if good.

Memory trick: Clamp the hose, feel the squeeze; if the pedal's firm, you're at ease (with your diagnosis).

A restricted brake line or hose impedes the flow of hydraulic fluid, leading to symptoms such as inconsistent fluid flow during bleeding, pulling to one side during braking, or a wheel dragging after pedal release. This occurs despite normal system pressure.

• Inconsistent fluid flow.
• Steady pressure applied.
• Can be hard line or flexible hose.
• Causes uneven braking.

Memory trick: Fluid's trying to pass, but a hidden block's in its class.

Reasons why a flare nut connection on a brake line might leak, focusing on installation errors.

• Proper torque is crucial for a leak-free seal.
• Under-tightening allows seepage.
• Over-tightening can damage the flare itself.

Memory trick: Flare leaks: too loose to seal, or too tight to hold.

The process of setting the brake shoes' distance from the drum, crucial for proper pedal height and effective braking in drum brake systems.

• Manual or automatic adjusters.
• Incorrect adjustment leads to low pedal or excessive travel.
• Must be checked after brake service or often during inspection.

Memory trick: Low pedal woes, check drum shoes.

Deburring the inside and outside edges of a cut brake line is a critical step before flaring to ensure a smooth, concentric, and crack-free flare.

• Cutting a brake line creates burrs on the edges.
• Internal burrs interfere with material flow during flaring.
• Burrs can cause uneven, weak, or cracked flares.
• Proper deburring ensures a strong, leak-free connection.

Memory trick: A rough edge makes a rough flare; smooth it first.

A threaded valve on a brake caliper or wheel cylinder, used to release air and old fluid from the hydraulic system during bleeding.

• Must be sealed to prevent air intrusion.
• Opened to release fluid/air, closed to prevent air entry.
• Improper sealing causes air to be drawn in.

Memory trick: Loose screw, air will accrue, tighten it true.

DOT 5 (silicone-based) brake fluid is non-hygroscopic, but it has a tendency to aerate, meaning it can trap air bubbles more easily than glycol-based fluids. These trapped air bubbles can cause a spongy brake pedal and make the fluid appear cloudy, requiring careful bleeding procedures.

• Silicone-based.
• Non-hygroscopic.
• Prone to air entrapment/aeration.
• Causes spongy pedal.

Memory trick: DOT 5's cloudy, air's aloud, making the pedal a spongy shroud!

A diagnostic procedure to check the functionality of a vacuum brake booster by observing pedal movement when the engine is started with the pedal depressed.

• Deplete vacuum with engine off
• Hold pedal, start engine
• Pedal should drop slightly if functional

Memory trick: Engine on, pedal drops, booster's working, the assist never stops!

An electric motor within the ABS Hydraulic Control Unit (HCU) that rapidly cycles to generate and release hydraulic pressure to individual wheels during anti-lock braking events.

• Responsible for pressure modulation during ABS events.
• Failure can lead to a hard pedal during ABS activation.
• Often controlled by the ABS control module.

Memory trick: ABS hard pedal, motor not pumping, wheels not stopping.

An internal bypass in a master cylinder occurs when the primary or secondary piston seals fail, allowing brake fluid to leak past them instead of building hydraulic pressure. This results in a soft, spongy pedal and reduced braking effectiveness.

• Pedal feels soft/spongy.
• Fluid bypasses piston seals.
• No external leaks.
• Poor fluid expulsion during bleeding.

Memory trick: When the master cylinder's seals are beat, the brake fluid can't make the pressure meet.

A one-way valve located in the vacuum line to the brake booster, designed to maintain vacuum within the booster even when the engine is off.

• Ensures power assist for initial brake applications after engine is shut off.
• Failure leads to loss of vacuum in the booster.
• Symptom of failure is a hard brake pedal requiring excessive effort.

Memory trick: Hard pedal? Booster's not boosting, or something's blocking.

The comparison of hydraulic pressure between the primary and secondary circuits of a dual master cylinder, used to diagnose system imbalances.

• Pressures should be nearly equal in a healthy system.
• Significant differences indicate issues like leaks, air, or component wear in the lower-pressure circuit.
• Typically measured with pressure gauges at the wheel cylinders/calipers.

Memory trick: Pressure balance tells the tale, circuits should be equally hale.

A valve, often part of the quick take-up valve or master cylinder, that maintains a small amount of hydraulic pressure in the brake lines (typically 5-10 PSI) after the brake pedal is released, to keep brake shoes/pads close to the drums/rotors.

• Minimizes pedal travel
• Ensures quick brake response
• Prevents air from entering system through seals

Memory trick: Residual pressure, keep it tight, so your pedal feels just right!

Internal deterioration of a flexible brake hose causing it to expand or bulge under hydraulic pressure, reducing effective pressure to the caliper.

• Caused by internal hose damage/age.
• Absorbs hydraulic pressure, weakening brake.
• Leads to uneven braking and pulling.

Memory trick: Bulging hose, pressure goes, pull it shows.

An active (powered) wheel speed sensor that outputs a false, consistent signal (e.g., a constant frequency) even when the wheel is stationary. This is typically due to an internal electronic fault or a short within the sensor itself.

• Occurs with active (powered) sensors.
• False signal generated when stationary.
• Indicates internal sensor failure or short.

Memory trick: Still Wheel, False Pulse: Sensor's Lies!

The process of configuring a new or replacement ABS control module with vehicle-specific data and sensor calibration values to ensure correct operation.

• Often requires a specialized scan tool.
• Includes VIN, tire size, sensor offsets, and sometimes variant coding.
• Failure to program/calibrate can lead to improper ABS function without DTCs.

Memory trick: New brains need new training; without it, they're just confused.

An open circuit in a passive wheel speed sensor's internal coil means there's a break in the wire, preventing it from generating an AC voltage signal. This results in an infinite resistance reading during testing.

• Passive WSS has an internal coil.
• Resistance test checks coil integrity.
• Open circuit = infinite resistance = failed sensor.

Memory trick: Resistance Check: Open = Broken Coil!

A failure mode in an active wheel speed sensor where its digital output signal remains at a constant high voltage level.

• Prevents the ABS module from detecting a valid frequency (wheel speed).
• Interpreted as an implausible or faulty signal by the module.
• Often triggers specific diagnostic trouble codes for sensor malfunction.

Memory trick: Stuck high, no square wave to tell, the module knows something's not well!

A sensor that measures the rotational velocity of a vehicle around its vertical axis (yaw). This input is vital for Electronic Stability Control (ESC) systems to detect and correct oversteer or understeer.

• Measures degrees per second of rotation.
• Often integrated with the lateral accelerometer.
• Critical for ESC system operation.

Memory trick: ESC's Eye: Yaw, Steer, Speed, G-Force, Brake!

An active safety system that prevents loss of traction of driven wheels by detecting wheel spin and applying corrective measures.

• Uses wheel speed sensors to detect differences in wheel speed.
• Primarily applies brakes to slipping wheels and/or reduces engine power.
• Helps maintain stability during acceleration on slippery surfaces.

Memory trick: When wheels spin, TCS steps in, braking and cutting power to win!

Troubleshooting an electrical fault with the ABS hydraulic pump motor.

• A C0110 code indicates a circuit malfunction.
• Always start by verifying power and ground to the ABS module.
• The pump motor is critical for recirculating fluid and building pressure during ABS events.

Memory trick: Pump motor circuit fault? Check the module's power first, before you start to shout!

The precise distance between a passive wheel speed sensor and its tone ring, critical for generating a strong and accurate AC voltage signal.

• Too large an air gap reduces signal strength.
• Too small an air gap can cause physical contact and damage.
• Incorrect air gap often results in 'Range/Performance' fault codes.

Memory trick: Air gaps can make a sensor 'act' faulty, even if its wires are fine.

Damage to vehicle wiring caused by rodents, often leading to various electrical circuit issues.

• Commonly causes high resistance due to partial conductor damage or corrosion.
• Can also lead to open circuits (complete breaks) or shorts (to ground or power).
• Often results in intermittent or incorrect sensor signals and related DTCs.

Memory trick: Chewed wires can be a real fright, making resistance high or signal not right!

The brake pressure sensor measures the hydraulic pressure in the brake lines, providing critical input to the ABS and ESC modules. This data helps the systems understand the driver's braking intent and precisely control brake application.

• Measures hydraulic pressure.
• Input for ABS and ESC.
• Located in HCU or brake lines.

Memory trick: Pressure Sensor: ESC's Hydraulic Eyes!

The air gap between a wheel speed sensor (WSS) and its tone ring is critical for accurate signal generation. An incorrect or excessive air gap can lead to erratic or absent speed readings.

• Too large an air gap weakens the signal.
• Too small an air gap can cause physical damage.
• Affects passive and active WSS differently but both require proper spacing.

Memory trick: Sensor's Gap: Too Far, No Star!

The impact of the distance between a passive magnetic wheel speed sensor and its tone ring on the generated signal.

• An inverse relationship exists: larger gap = weaker magnetic field.
• Weaker magnetic field results in lower induced AC voltage.
• Excessive gaps can lead to intermittent or no signal, triggering DTCs.

Memory trick: Gap too big, signal too small, that's the magnetic sensor's fall!

In vehicles using engine vacuum or a dedicated electric pump for brake assist, the Power Assist Unit (PAU) or vacuum pump generates the necessary vacuum for the brake booster. A failure results in a 'hard' pedal and reduced braking efficiency.

• Provides vacuum for brake booster.
• Failure causes hard pedal, extended stopping.
• Crucial for modern braking systems.

Memory trick: Hard Pedal: Think Vacuum Power!

Troubleshooting a diagnostic trouble code (DTC) indicating a problem with the electrical power supply to a wheel speed sensor.

• Often involves checking voltage at the sensor connector.
• 0 volts on the supply wire points to wiring issues or module output failure.
• A common next step is to inspect the wiring harness for opens or shorts.

Memory trick: No power to the sensor? Trace the wire, don't just replace!

The typical location of the sensor that measures hydraulic brake pressure for the Anti-lock Brake System (ABS) and Electronic Stability Control (ESC).

• Essential for ESC to monitor driver brake input and system response.
• Almost exclusively integrated within the ABS hydraulic control unit (HCU).
• A malfunction results in diagnostic trouble codes like C1288.

Memory trick: Pressure sensor's heart, in the HCU it's a part!

Electrically controlled valves within the Hydraulic Control Unit (HCU) that are responsible for precisely modulating hydraulic pressure to individual wheel brake circuits. They are crucial for ABS, TCS, and ESC operations.

• Open, close, or hold pressure.
• Controlled by ABS/TCS/ESC module.
• Directly actuate braking force on wheels.

Memory trick: TCS Brake: Solenoids are the Pressure Pilots!

A sensor that measures the absolute angular position and often the rate of rotation of the steering wheel. It provides the ABS/ESC control module with the driver's intended direction of travel, which is crucial for stability control calculations.

• Measures steering wheel position.
• Indicates driver's intended path.
• Critical input for ESC and traction control.

Memory trick: SAS: ESC's Intent Interpreter!

Using tires of different rolling circumferences on a vehicle, particularly on the same axle, can lead to incorrect wheel speed sensor readings. The ABS module may misinterpret these discrepancies as wheel slip, causing premature or erratic ABS activation.

• Causes rotational speed differences.
• Confuses ABS/TCS/ESC modules.
• Can lead to false ABS activations without codes.

Memory trick: ABS Pulse: Check the Tires' Roll!

Electronic Stability Control's method to counteract a vehicle's rear end sliding outwards in a turn.

• Detects oversteer using yaw rate, steering angle, and wheel speed sensors.
• Primarily applies brake to the outside front wheel.
• Creates a counter-yaw moment to bring the vehicle back in line.

Memory trick: Oversteer is a spin, so brake the outer front to pull it back in!

An interruption in the electrical path of a wheel speed sensor, preventing it from sending a signal to the ABS control module.

• Causes a 0 MPH reading from the affected sensor when the wheel is rotating.
• Often triggers specific diagnostic trouble codes (DTCs) for that sensor.
• Can be caused by damaged wiring, corroded connectors, or a faulty sensor itself.

Memory trick: When the wheel stops sending speed, check the wiring for a break in the lead!

Methods used to diagnose a faulty ABS control module, distinguishing between feasible and unfeasible approaches.

• Modern modules are sealed, not designed for internal repair.
• Diagnosis focuses on external electrical checks, scan tool data, and DTCs.
• Disassembly for visual inspection is generally not recommended or practiced.

Memory trick: ABS brain's sealed, don't break it open, check outside, keep hope open!

The electrical relay that controls the power supply to the solenoid valves within the ABS hydraulic control unit.

• Crucial for modulating brake pressure during ABS activation.
• Almost universally integrated into the ABS hydraulic control unit (HCU) or ABS module assembly.
• A malfunction causes a C0121 fault code, indicating a circuit issue.

Memory trick: The ABS valve relay is like the heart's switch, right inside the hydraulic ditch!

The ideal percentage of wheel slip that an ABS system aims to maintain during braking for maximum stopping power and control.

• Typically ranges from 10% to 20% slip.
• Achieves the highest coefficient of friction between tire and road.
• Prevents full wheel lock-up, maintaining steerability during hard braking.

Memory trick: For the best stop, a little slip is the top crop (10-20 percent, not a flop)!

A procedure using a diagnostic scan tool to actuate the ABS pump and solenoid valves, forcing air out of the hydraulic control unit.

• Necessary after replacing ABS HCU, master cylinder, or extended system opens.
• Traditional bleeding methods cannot remove air from internal ABS components.
• Ensures proper brake pressure modulation and prevents a spongy pedal.

Memory trick: After a module swap, bleed the air with the scan tool's clap!

In many contemporary ABS systems, the high-current relay that powers the ABS pump motor is integrated directly into the ABS control module, which is typically part of the hydraulic control unit (HCU) assembly.

• Often not a separately replaceable component.
• Simplifies wiring and packaging.
• Requires replacement of the entire module/HCU if the relay fails.

Memory trick: Pump Power: Module's Built-in Brain!

For critical electronic control modules like ABS, the maximum allowable voltage drop across power or ground circuits from the battery/ground point to the module should generally not exceed 0.1 volts (100mV).

• Ensures adequate voltage supply.
• Higher drop indicates excessive resistance.
• Critical for sensitive electronics.

Memory trick: ABS Power: Max Drop is a Tenth!

Corrosion in electrical connectors, especially those exposed to environmental factors, can lead to intermittent circuit issues, high resistance, and signal loss. This often manifests as intermittent fault codes in electronic systems like ABS.

• Increases resistance in the circuit.
• Causes intermittent signal disruptions.
• Worsens with moisture exposure.

Memory trick: Rainy Day Faults: Check the Module's Plug!

The process of setting the correct tension in the parking brake cable to ensure proper engagement and holding power with appropriate lever travel.

• Prevents excessive lever travel.
• Ensures adequate holding force.
• Performed at the equalizer or cable ends.

Memory trick: Cable too loose, parking's no use, adjust the noose.

After addressing mechanical issues with parking brake components (like seized levers), the parking brake cable tension must be adjusted to ensure proper operation and holding power.

• Ensures effective holding
• Corrects cable slack
• Follows mechanical repair

Memory trick: Fix the parts, then set the tension, then test the retention.

Diagnosing a brake pull involves identifying which brake is over-applying or under-applying, often by checking drum/rotor temperature and inspecting components for issues like seized calipers/wheel cylinders or contaminated friction material.

• Pulling indicates an imbalance in braking force.
• Hotter drum/rotor indicates the side doing more work (dragging or over-applying).
• Cooler drum/rotor indicates the side is under-applying.

Memory trick: Temp Tells the Tale of the Pulling Trail

Uneven wear between primary and secondary drum brake shoes can indicate issues with specific components, such as seized wheel cylinder pistons, weak return springs, or contamination affecting one shoe more than the other.

• Primary shoe usually wears faster due to self-energization.
• Excessive wear on primary can indicate dragging.
• Excessive wear on secondary can indicate various issues like weak spring or contamination.

Memory trick: Primary's Piston Stuck, Friction's Luck

The process of visually and dimensionally checking a brake drum for wear, damage, and specified limits to ensure safe and effective braking.

• Check for scoring, cracks, and heat checking.
• Measure drum diameter for wear and runout.
• Compare measurements to manufacturer specifications for maximum diameter.

Memory trick: See the damage, measure the limit, then fix or ditch it.

A fixed post mounted on the backing plate of a drum brake system that provides a stationary pivot point for the top ends of the brake shoes.

• Crucial for proper shoe expansion and self-energization.
• Top ends of primary and secondary shoes rest against it.
• Ensures shoes remain centered and stable during braking.

Memory trick: The anchor pin, at the top, helps the shoes pivot and stop.

Pitting in a wheel cylinder bore is corrosion that creates small depressions, compromising the sealing surface for the rubber cups and leading to potential fluid leaks.

• Compromises seal integrity.
• Can lead to brake fluid leaks.
• Replacement is generally recommended.

Memory trick: Pits in the bore, safety's no more, replace it, for sure.

Drum brake shoes are differentiated by their position and lining material, affecting their role in the self-energizing braking action.

• Primary shoe: faces forward, less lining, initiates contact.
• Secondary shoe: faces rearward, more lining, provides main braking force due to self-energization.
• Self-energization: rotation of the drum pulls primary shoe into drum, which then pushes secondary shoe harder.

Memory trick: Primary leads the way, secondary does the heavy work, always remember the lining play.

Indicators of excessive heat buildup in a braking system, including visual changes to components and changes in pedal feel and braking performance.

• Visual: glazed shoes, discolored/heat-spotted drums/rotors.
• Feel: 'grabby' or 'hard' pedal, brake fade.
• Causes: excessive braking, dragging brakes, incorrect material.

Memory trick: Hot brakes make shoes hard and glazed, and the pedal will feel amazed (or bad!).

The presence of oil, grease, or brake fluid on the friction material of a brake shoe, significantly reducing its coefficient of friction and braking effectiveness.

• Causes: leaking wheel cylinder, leaking axle seal, improper lubrication.
• Symptoms: reduced braking efficiency, pulling to one side, spongy pedal if fluid leak is severe.
• Remedy: replace contaminated shoes and repair the source of the leak.

Memory trick: Grease on a shoe means less grip, so the car will pull to the other hip.

Excessive slack in the parking brake cable reduces the mechanical advantage, requiring more lever travel to engage the parking brake shoes against the drum.

• Leads to weak parking brake.
• Requires more lever travel.
• Adjustable to restore function.

Memory trick: Cable too long, parking brake's song is weak and wrong.

Surface rust and corrosion on a brake drum's friction surface can cause noise, reduced braking effectiveness, and premature wear of brake shoes. It often requires resurfacing or replacement.

• Common on vehicles stored or driven in humid conditions.
• Causes grinding noise and reduced friction.
• Must be removed by machining or drum replacement.

Memory trick: Rust on Drum, Turn it Some (or Replace, if Done)