In-Cab Parts

Question 1

Safety Belt

Answer 1

A vehicle safety device designed to secure the driver or a passenger of a vehicle against harmful movement that may result during a collision or a sudden stop.

Question 2

Fire Extinguisher

Answer 2

A handheld active fire protection device usually filled with a dry or wet chemical used to extinguish or control small fires, often in emergencies.

Question 3

Reflective Triangles

Answer 3

Reflective triangles provide visibility for the truck and driver to other motorists during an emergency stop.
The first step is to turn on the four-way flashers before putting out emergency triangles.
Emergency triangles must be placed within 10 minutes of stopping and should be kept in the passenger side box so they can be accessed in a way that keeps the driver away from traffic.
The following are the most common emergency triangle placements for truck drivers

Question 4

Two Lane (Traffic in both directions and undivided highways)

Answer 4

One triangle 100 feet in front of the vehicle, centered in the lane the vehicle occupies.
One triangle 10 feet behind the vehicle on the traffic side of the vehicle.
One triangle 100 feet behind the vehicle in the center of the lane the vehicle occupies.

Question 5

Divided Highways and one-way roads

Answer 5

One triangle 10 feet behind the vehicle on the traffic side of the vehicle.
One triangle 100 feet behind the vehicle in the center of the lane the vehicle occupies.
One triangle 200 feet behind the vehicle in the center of the lane it occupies.

Question 6

Obstructed views (hills and curves)

Answer 6

Place one triangle at least 100 feet ahead of the vehicle.
One triangle should be placed at least 10 feet behind the vehicle on the traffic side of the vehicle.
Move the rearmost triangle between 100 feet and 500 feet back down the road to provide ample warning (the maximum distance from the vehicle shall not exceed 500 feet)

Question 7

Spare Fuses

Answer 7

The Department of Transportation (DOT) establishes minimum standards for commercial motor vehicles.
The regulations require emergency equipment on all power units.
Power units for which fuses are needed to operate any required parts and accessories must have at least one spare fuse for each type and size of fuse needed for those parts and accessories (49CFR 393.95(b)).

Question 8

Ignition Key

Answer 8

The key of an ignition serves two purposes:
It ensures that only the person who carries the keys can start the car and drive it away, and it not only starts the engine but activates all the other electronic and mechanical systems in the vehicle.

Question 9

Accessory mode

Answer 9

Accessory mode operates some accessories on battery power while the engine is turned off.

Question 10

Anti-lock braking system

Answer 10

An anti-lock braking system (ABS) is a safety anti-skidding braking system used on aircraft and on some land vehicles such as cars, motorcycles, trucks, and buses.
ABS operates by preventing the wheels from locking up during braking, thereby maintaining tractive contact with the road surface and allowing the driver to maintain more control over the vehicle.

Question 11

Early Antilock braking systems example (1920)

Answer 11

In 1920 the French automobile and aircraft pioneer Gabriel Voisin experimented with systems that modulated the hydraulic braking pressure on his aircraft brakes to reduce the risk of tire slippage, as threshold braking on aircraft is nearly impossible. These systems used a flywheel and valve attached to a hydraulic line that feeds the brake cylinders. The flywheel is attached to a drum that runs at the same speed as the wheel. In normal braking, the drum and flywheel should spin at the same speed. However, when a wheel slows down, then the drum would do the same, leaving the flywheel spinning at a faster rate. This causes the valve to open, allowing a small amount of brake fluid to bypass the master cylinder into a local reservoir, lowering the pressure on the cylinder and releasing the brakes. The use of the drum and flywheel meant the valve only opened when the wheel was turning. In testing, a 30% improvement in braking performance was noted, because the pilots immediately applied full brakes instead of slowly increasing pressure in order to find the skid point. An additional benefit was the elimination of burned or burst tires.

Question 12

ABS 1928 - 1971

Answer 12

The first proper recognition of the ABS system came later with the German engineer Karl Wässel, whose system for modulating braking power was officially patented in 1928. Wässel, however, never developed a working product and neither did Robert Bosch who produced a similar patent eight years later.[5]

A similar braking system called Decelostat that used direct-current generators to measure wheel slippage was used in railroads in the 1930s.[7] By 1951, flywheel-based Decelostat was used in aircraft to provide anti skid in landings. The device was on trials first in the United States and later by the British.[8] In 1954, Popular Science revealed that there was preliminary testing of the Decelostat system to prevent car swirling on a heavy brake by the US car manufacturers in Detroit. However, there was no public information of the test results.[9]

By the early 1950s, the Dunlop Maxaret anti-skid system was in widespread aviation use in the UK, with aircraft such as the Avro Vulcan and Handley Page Victor, Vickers Viscount, Vickers Valiant, English Electric Lightning, de Havilland Comet 2c, de Havilland Sea Vixen, and later aircraft, such as the Vickers VC10, Hawker Siddeley Trident, Hawker Siddeley 125, Hawker Siddeley HS 748 and derived British Aerospace ATP, and BAC One-Eleven, and the Dutch Fokker F27 Friendship (which unusually had a Dunlop high pressure (200 Bar) pneumatic system in lieu of hydraulics for braking, nose wheel steering and landing gear retraction), being fitted with Maxaret as standard.[10] Maxaret, while reducing braking distances by up to 30% in icy or wet conditions, also increased tire life, and had the additional advantage of allowing take-offs and landings in conditions that would preclude flying at all in non-Maxaret equipped aircraft.

In 1958, a Royal Enfield Super Meteor motorcycle was used by the Road Research Laboratory to test the Maxaret anti-lock brake.[11] The experiments demonstrated that anti-lock brakes can be of great value to motorcycles, for which skidding is involved in a high proportion of accidents. Stopping distances were reduced in most of the tests compared with locked wheel braking, particularly on slippery surfaces, in which the improvement could be as much as 30%. Enfield’s technical director at the time, Tony Wilson-Jones, saw little future in the system, however, and it was not put into production by the company.[11]

A fully-mechanical system saw limited automobile use in the 1960s in the Ferguson P99 racing car, the Jensen FF, and the experimental all-wheel drive Ford Zodiac, but saw no further use; the system proved expensive and unreliable.

The first fully-electronic anti-lock braking system was developed in the late-1960s for the Concorde aircraft.

The modern ABS system was invented in 1971 by Mario Palazzetti (known as ‘Mister ABS’) in the Fiat Research Center and is now standard in almost every car. The system was called Antiskid and the patent was sold to Bosch who named it ABS.[12]

Question 13

Modern ABS

Answer 13

Modern systems
Chrysler, together with the Bendix Corporation, introduced a computerized, three-channel, four-sensor all-wheel[13] ABS called “Sure Brake” for its 1971 Imperial.[14] It was available for several years thereafter, functioned as intended, and proved reliable. In 1969, Ford introduced an anti-lock braking system called “Sure-Track” to the rear wheels of the Lincoln Continental Mark III and Ford Thunderbird, as an option;[15] it became standard in 1971.[16] The Sure-Track braking system was designed with help from Kelsey-Hayes. In 1971, General Motors introduced the “Trackmaster” rear-wheel only[17] ABS as an option on their rear-wheel drive Cadillac models[18][19] and called the option the True-Track Braking System on the Oldsmobile Toronado.[20] In 1972, the option was made available in all Cadillacs. In 1971, Nissan offered an EAL (Electro Anti-lock System) developed by Japanese company Denso as an option on the Nissan President, which became Japan’s first electronic ABS.[21]

1971: The Imperial [22] became the first production car with a 4 wheel computer-operated anti-lock braking system. Toyota introduced electronically controlled anti-skid brakes on Toyota Crown.[23]

1971: First truck application: “Antislittamento” system developed by Fiat Veicoli Industriali and installed on Fiat truck model 691N1.[24]

1972: four-wheel-drive Triumph 2500 Estates were fitted with Mullard electronic systems as standard.[citation needed] Such cars were very rare however and very few survive today.

1976: WABCO began the development of the anti-locking braking system on commercial vehicles to prevent locking on slippery roads, followed in 1986 by the electronic braking system (EBS) for heavy-duty vehicles.[25]

1978: Mercedes-Benz W116 As one of the firsts, used an electronic four-wheel multi-channel anti-lock braking system (ABS) from Bosch as an option from 1978 on.

1982: Honda introduced electronically controlled multi-channel ALB (Anti Locking Brakes) as an option for the second generation of Prelude, launched worldwide in 1982. Additional info: the general agent for Honda in Norway required all Preludes for the Norwegian market to have the ALB-system as a standard feature, making Honda Prelude be the first car delivered in Europe with ABS as a standard feature. The Norwegian general agent also included a sunroof and other options to be standard equipment in Norway, adding more luxury to the Honda brand. However, the Norwegian tax system made the well-equipped car very expensive, and the sales suffered from high costs. From 1984 the ALB-system, as well as the other optional features from Honda, was no longer a standard feature in Norway.

In 1985 the Ford Scorpio was introduced to the European market with a Teves electronic system throughout the range as standard. For this the model was awarded the coveted European Car of the Year Award in 1986, with very favorable praise from motoring journalists. After this success, Ford began research into Anti-Lock systems for the rest of their range, which encouraged other manufacturers to follow suit.

Since 1987 ABS has been standard equipment on all Mercedes-Benz automobiles.[26] Lincoln followed suit in 1993.[27]

In 1988, BMW introduced the first motorcycle with an electro-hydraulic ABS: the BMW K100. Yamaha Introduced the FJ1200 model with optional ABS in 1991. Honda followed suit in 1992 with the launch of its first motorcycle ABS on the ST1100 Pan European. In 2007, Suzuki launched its GSF1200SA (Bandit) with an ABS. In 2005, Harley-Davidson began offering an ABS option on police bikes.

Question 14

ABS Operation

Answer 14

Operation

The anti-lock brake controller is also known as the CAB (Controller Anti-lock Brake).[28]

Typically ABS includes a central electronic control unit (ECU), four wheel speed sensors, and at least two hydraulic valves within the brake hydraulics. The ECU constantly monitors the rotational speed of each wheel; if it detects the wheel rotating significantly slower than the speed of the vehicle, a condition indicative of impending wheel lock, it actuates the valves to reduce hydraulic pressure to the brake at the affected wheel, thus reducing the braking force on that wheel; the wheel then turns faster. Conversely, if the ECU detects a wheel turning significantly faster than the others, brake hydraulic pressure to the wheel is increased so the braking force is reapplied, slowing down the wheel. This process is repeated continuously and can be detected by the driver via brake pedal pulsation. Some anti-lock systems can apply or release braking pressure 15 times per second.
Because of this, the wheels of cars equipped with ABS are practically impossible to lock even during panic braking in extreme conditions.

The ECU is programmed to disregard differences in wheel rotative speed below a critical threshold because when the car is turning, the two wheels towards the center of the curve turn slower than the outer two. For this same reason, a differential is used in virtually all roadgoing vehicles.

If a fault develops in any part of the ABS, a warning light will usually be illuminated on the vehicle instrument panel, and the ABS will be disabled until the fault is rectified.

Modern ABS applies individual brake pressure to all four wheels through a control system of hub-mounted sensors and a dedicated micro-controller. ABS is offered or comes standard on most road vehicles produced today and is the foundation for electronic stability control systems, which are rapidly increasing in popularity due to the vast reduction in the price of vehicle electronics over the years.

Modern electronic stability control (ESC) systems are an evolution of the ABS concept. Here, a minimum of two additional sensors are added to help the system work: these are a steering wheel angle sensor and a gyroscopic sensor. The theory of operation is simple: when the gyroscopic sensor detects that the direction taken by the car does not coincide with what the steering wheel sensor reports, the ESC software will brake the necessary individual wheel(s) (up to three with the most sophisticated systems), so that the vehicle goes the way the driver intends. The steering wheel sensor also helps in the operation of Cornering Brake Control (CBC), since this will tell the ABS that wheels on the inside of the curve should brake more than wheels on the outside, and by how much.

ABS equipment may also be used to implement a traction control system (TCS) on the acceleration of the vehicle. If, when accelerating, the tire loses traction, the ABS controller can detect the situation and take suitable action so that traction is regained. More sophisticated versions of this can also control throttle levels and brakes simultaneously.

The speed sensors of ABS are sometimes used in indirect tire pressure monitoring system (TPMS), which can detect under-inflation of the tire(s) by the difference in the rotational speed of wheels.

Question 15

ABS Components

Answer 15

Components

There are four main components of ABS: wheel speed sensors, valves, a pump, and a controller.
Speed sensors (Encoders)
A speed sensor is used to determine the acceleration or deceleration of the wheel. These sensors use a magnet and a Hall effect sensor, or a toothed wheel and an electromagnetic coil to generate a signal. The rotation of the wheel or differential induces a magnetic field around the sensor. The fluctuations of this magnetic field generate a voltage in the sensor. Since the voltage induced in the sensor is a result of the rotating wheel, this sensor can become inaccurate at slow speeds. The slower rotation of the wheel can cause inaccurate fluctuations in the magnetic field and thus cause inaccurate readings to the controller.
Valves
There is a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions:

In position one, the valve is open; pressure from the master cylinder is passed right through to the brake.
In position two, the valve blocks the line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder.
In position three, the valve releases some of the pressure from the brake.

Partially disassembled four-channel hydraulic control unit containing motor, pump and valves

The majority of problems with the valve system occur due to clogged valves. When a valve is clogged it is unable to open, close, or change position. An inoperable valve will prevent the system from modulating the valves and controlling pressure supplied to the brakes.

Pump
The pump in the ABS is used to restore the pressure to the hydraulic brakes after the valves have released it. A signal from the controller will release the valve at the detection of wheel slip. After a valve releases the pressure supplied from the user, the pump is used to restore the desired amount of pressure to the braking system. The controller will modulate the pump’s status in order to provide the desired amount of pressure and reduce slipping.
Controller
The controller is an ECU type unit in the car which receives information from each individual wheel speed sensor. If a wheel loses traction, the signal is sent to the controller. The controller will then limit the brake force (EBD) and activate the ABS modulator which actuates the braking valves on and off.

Question 16

ABS Control Algorithm Use

Answer 16

Use

There are many different variations and control algorithms for use in ABS. One of the simpler systems works as follows:[30]

The controller monitors the speed sensors at all times. It is looking for decelerations in the wheel that are out of the ordinary. Right before a wheel locks up, it will experience a rapid deceleration. If left unchecked, the wheel would stop much more quickly than any car could. It might take a car two to four seconds to stop from 60 mph (96.6 km/h) under ideal conditions, but a wheel that locks up could stop spinning in less than a second.
The ABS controller knows that such a rapid deceleration of the car is impossible (and in actuality the rapid deceleration means the wheel is about to slip), so it reduces the pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the deceleration again. It can do this very quickly before the wheel can actually significantly change speed. The result is that the wheel slows down at the same rate as the car, with the brakes keeping the wheels very near the point at which they will start to lock up. This gives the system maximum braking power.
This replaces the need to manually pump the brakes while driving on a slippery or a low traction surface, allowing to steer even in most emergency braking conditions.
When the ABS is in operation the driver will feel a pulsing in the brake pedal; this comes from the rapid opening and closing of the valves. This pulsing also tells the driver that the ABS has been triggered.

Question 17

ABS Brake Types

Answer 17

Brake types

Anti-lock braking systems use different schemes depending on the type of brakes in use. They can be differentiated by the number of channels: that is, how many valves that are individually controlled—and the number of speed sensors.[30]

1) Four-channel, four-sensor ABS
There is a speed sensor on all four wheels and a separate valve for all four wheels. With this setup, the controller monitors each wheel individually to make sure it is achieving maximum braking force.
2) Three-channel, four-sensor ABS
There is a speed sensor on all four wheels and a separate valve for each of the front wheels, but only one valve for both of the rear wheels. Older vehicles with four-wheel ABS usually use this type.
3) Three-channel, three-sensor ABS
This scheme, commonly found on pickup trucks with four-wheel ABS, has a speed sensor and a valve for each of the front wheels, with one valve and one sensor for both rear wheels. The speed sensor for the rear wheels is located in the rear axle. This system provides individual control of the front wheels, so they can both achieve maximum braking force. The rear wheels, however, are monitored together; they both have to start to lock up before the ABS will activate on the rear. With this system, it is possible that one of the rear wheels will lock during a stop, reducing brake effectiveness. This system is easy to identify, as there are no individual speed sensors for the rear wheels.
4) Two-channel, four-sensor ABS
This system, commonly found on passenger cars from the late ’80s through the mid-1990s, uses a speed sensor at each wheel, with one control valve each for the front and rear wheels as a pair. If the speed sensor detects lock up at any individual wheel, the control module pulses the valve for both wheels on that end of the car.
5) One-channel, one-sensor ABS
This system is commonly found on pickup trucks, SUVs, and vans with rear-wheel ABS. It has one valve, which controls both rear wheels, and a one-speed sensor, located in the rear axle. This system operates the same as the rear end of a three-channel system. The rear wheels are monitored together and they both have to start to lock up before the ABS kicks in. In this system it is also possible that one of the rear wheels will lock, reducing brake effectiveness. This system is also easy to identify, as there are no individual speed sensors for any of the wheels.

Question 18

ABS Effectiveness

Answer 18

Effectiveness

A 2004 Australian study by Monash University Accident Research Centre found that ABS:[2]

Reduced the risk of multiple vehicle crashes by 18 percent,
Increased the risk of run-off-road crashes by 35 percent.

On high-traction surfaces such as bitumen, or concrete, many (though not all) ABS-equipped cars are able to attain braking distances better (i.e. shorter) than those that would be possible without the benefit of ABS. In real-world conditions, even an alert and experienced driver without ABS would find it difficult to match or improve on the performance of a typical driver with a modern ABS-equipped vehicle. ABS reduces the chances of crashing, and/or the severity of impact. The recommended technique for non-expert drivers in an ABS-equipped car, in a typical full-braking emergency, is to press the brake pedal as firmly as possible and, where appropriate, to steer around obstructions. In such situations, ABS will significantly reduce the chances of a skid and subsequent loss of control.

In gravel, sand, and deep snow, ABS tends to increase braking distances. On these surfaces, locked wheels dig in and stop the vehicle more quickly. ABS prevents this from occurring. Some ABS calibrations reduce this problem by slowing the cycling time, thus letting the wheels repeatedly briefly lock and unlock. Some vehicle manufacturers provide an “off-road” button to turn the ABS function off. The primary benefit of ABS on such surfaces is to increase the ability of the driver to maintain control of the car rather than go into a skid, though the loss of control remains more likely on soft surfaces such as gravel or on slippery surfaces such as snow or ice. On a very slippery surface such as sheet ice or gravel, it is possible to lock multiple wheels at once, and this can defeat ABS (which relies on comparing all four wheels and detecting individual wheels skidding). The availability of ABS relieves most drivers from learning threshold braking.

A June 1999 National Highway Traffic Safety Administration (NHTSA) study found that ABS increased stopping distances on loose gravel by an average of 27.2 percent.[32]

According to the NHTSA,

"ABS works with your regular braking system by automatically pumping them. In vehicles not equipped with ABS, the driver has to manually pump the brakes to prevent wheel lockup. In vehicles equipped with ABS, your foot should remain firmly planted on the brake pedal, while ABS pumps the brakes for you so you can concentrate on steering to safety."

When activated, some earlier ABSes caused the brake pedal to pulse noticeably. As most drivers rarely or do not brake hard enough to cause brake lock-up, and drivers typically do not read the vehicle’s owner’s manual, this may not be noticeable until an emergency. Some manufacturers have therefore implemented a brake assist system that determines that the driver is attempting a “panic stop” (by detecting that the brake pedal was depressed very quickly, unlike a normal stop where the pedal pressure would usually be gradually increased. Some systems additionally monitor the rate at the accelerator was released, and/or the time between accelerator release and brake application)[citation needed] and the system automatically increases braking force where not enough pressure is applied. Hard or panic braking on bumpy surfaces, because of the bumps causing the speed of the wheel(s) to become erratic may also trigger the ABS, sometimes causing the system to enter its ice mode, where the system severely limits maximum available braking power. Nevertheless, ABS significantly improves safety and control for drivers in most on-road situations.

Anti-lock brakes are the subject of some experiments centred around risk compensation theory, which asserts that drivers adapt to the safety benefit of ABS by driving more aggressively. In a Munich study, half a fleet of taxicabs was equipped with anti-lock brakes, while the other half had conventional brake systems. The crash rate was substantially the same for both types of cab, and Wilde concludes this was due to drivers of ABS-equipped cabs taking more risks, assuming that ABS would take care of them, while the non-ABS drivers drove more carefully since ABS would not be there to help in case of a dangerous situation.

The Insurance Institute for Highway Safety released a study in 2010 that found motorcycles with ABS 37% less likely to be involved in a fatal crash than models without ABS.

Question 19

ABS Basic Principle

Answer 19

Basic principle
Wheel speed sensors mounted on the front and rear wheel constantly measures the rotational speed of each wheel and delivers this information to an Electronic Control Unit (ECU). The ECU detects two things: 1) if the deceleration of one wheel exceeds a fixed threshold and 2) whether the brake slip, calculated based on information of both wheels, rises above a certain percentage and enters an unstable zone. These are indicators for a high possibility of a locking wheel. To countermeasure these irregularities the ECU signals the hydraulic unit to hold or to release pressure. After signals show the return to the stable zone, the pressure is increased again. Past models used a piston for the control of the fluid pressure. Most recent models regulate the pressure by rapidly opening and closing solenoid valves. While the basic principle and architecture has been carried over from passenger car ABS, typical motorcycle characteristics have to be considered during the development and application processes. One characteristic is the change of the dynamic wheel load during braking. Compared to cars, the wheel load changes are more drastic, which can lead to a wheel lift up and a fall over. This can be intensified by a soft suspension. Some systems are equipped with a rear-wheel lift-off mitigation functionality. When the indicators of a possible rear lift-off are detected, the system releases brake pressure on the front wheel to counter this behavior. Another difference is that in the case of the motorcycle the front wheel is much more important for stability than the rear wheel. If the front wheel locks up between 0.2-0.7s, it loses gyrostatic forces and the motorcycle starts to oscillate because of the increased influence of side forces operating on the wheel contact line. The motorcycle becomes unstable and falls.

Question 20

Anti-lock Braking System

Answer 20

Anti-lock Braking System (ABS)

Piston Systems: The pressure release in this system is realized through the movement of a spring-tensioned piston. When pressure should be released, a linear motor pulls back the plunger piston and opens up more space for the fluid. The system was used for example in the ABS I (1988) and ABS II (1993) of BMW. The ABS II differed in size and an electronically controlled friction clutch was mounted on the shaft instead of a plunger. Further displacement sensors record the travel distance of the piston to allow the control unit a more precise regulation. Honda also uses this system of pressure modulation for big sports and touring bikes.[44][45]

Valve and Pump Systems: The main parts which are part of the pressure modulation system are solenoid inlet and outlet valves, a pump, motor, and accumulators/reservoirs. The number of the valves differs from model to model due to additional functionalities and the number of brake channels. Based on the input of the ECU, coils operate the inlet and outlet valves. During pressure release, the brake fluid is stored in accumulators. In this open system approach, the fluid is then brought back in the brake circuit via a pump operated by a motor that is felt through pulsation on the brake lever.

Question 21

US ABS Regulations

Answer 21

Laws and regulations
United States

In the United States, the NHTSA has mandated ABS in conjunction with electronic stability control under the provisions of FMVSS 126 as of September 1, 2012.

Question 22

Semi-Truck ABS

Answer 22

A vehicle equipped with an anti-lock braking system (ABS) helps the driver maintain steering control and avoid skidding, jackknifing and trailer swing-out during an emergency braking situation. When the brakes are applied, the ABS senses when a wheel is about to lock and then releases just enough brake force to get the wheel rolling again while still maintaining as much braking force on the wheel as possible. It may repeat this sequence several times a second and it may control each wheel differently.

Question 23

Identifying ABS Lamps

Answer 23

Know where the ABS lamp is on every vehicle you operate and how to check that it’s working properly. A yellow colored lamp, marked with the letters “ABS,” is located on the instrument panel of trucks, buses and truck tractors (dash-mounted), and located on the exterior of trailers, near the red side marker lamp on the left rear side (trailer-mounted). Converter dollies also have the lamp located on their left side. If the vehicle you drive was built after March 1, 2001, and it is equipped to tow a trailer, it will actually have two ABS lamps on the dash – one for the tractor (or truck) and one for the vehicles being towed.

Question 24

How ABS Works

Answer 24

When power is supplied to the trailer ABS unit, by the ignition switch being turned on (for ABS required power units) or by applying the brake pedal (for non-ABS required units), the lamp on the trailer momentarily turns on to indicate the ABS is working. During this time a self-test of the ABS is automatically conducted. When an ABS malfunction is detected during this test, the lamp stays on; otherwise, the lamp turns off after a few seconds. If the lamp does not come on during the self-test, there could be a problem with the lamp bulb, the wiring or the ABS controller.

If the light stays on during the self-test or comes on as the vehicle is being driven, there is an ABS malfunction. Make sure any problems found are fixed as quickly as possible. Remember, if the lamp does not work, the driver will never know if the ABS stops working.

Question 25

Verify ABS is Working

Answer 25

If your vehicle or combination includes any units that were required to be anti-lock brake system (ABS) equipped at the time of manufacture, those unit(s) must have a functioning ABS malfunction lamp(s) that turns on and then off when power is supplied to the unit. If ABS lamps do not illuminate at all, you likely have a violation. If ABS lamps illuminate and stay on, you also have a violation.