Question 1

The red brake warning lamp is on and the amber ABS lamp is off. Technician A says that a fault is possible in the base brake system. Technician B says that the red brake warning lamp can be turned on by a low brake fluid level in the master cylinder. Which technician is correct?

Accepted Answer

Both technicians are correct. The red brake warning lamp indicates a possible fault in the base brake system, as Technician A suggests. Technician B is also correct in stating that a low brake fluid level in the master cylinder can trigger the red brake warning lamp.

Question 2

Two technicians are discussing magnetic-type wheel speed sensors. Technician A says that 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 wheel speed sensors often use a magnetic field to detect wheel speed, but the toothed sensor ring itself is typically not magnetic; it is made of a ferrous material that disturbs the magnetic field as the wheel rotates, which the sensor detects.

Question 3

Technician A says that using the space saving small spare tire may trigger an ABS amber warning lamp. Technician B says the use of the small spare tire on either front wheel may trigger the red brake warning lamp. Which technician is correct?

Accepted Answer

Technician A is correct because using a smaller spare tire can affect the wheel speed sensor readings, potentially triggering the ABS warning lamp due to the discrepancy in wheel rotation speeds. Technician B's statement about triggering the red brake warning lamp is incorrect, as this lamp is typically related to the hydraulic brake system issues, not the use of a spare tire.

Question 4

Technician A says that, with some antilock braking systems, the diagnostic trouble code may be lost if the ignition is turned off before retrieving the code. Technician B says that some antilock braking systems require that a terminal be grounded to cause the amber ABS warning lamp to flash diagnostic trouble codes. Which technician is correct?

Accepted Answer

Both statements are accurate. Technician A is correct because certain antilock braking systems (ABS) can lose the stored diagnostic trouble codes (DTCs) if the ignition is turned off before the codes are retrieved. Technician B is correct because, in some ABS systems, grounding a specific terminal is a method used to trigger the ABS warning lamp to flash the DTCs.

Question 5

Technician A says that a scan tool may be required to retrieve data and diagnostic trouble codes from some antilock braking systems. Technician B says that a jumper wire can be used to retrieve diagnostic codes on some antilock braking systems. Which technician is correct?

Accepted Answer

Both statements are correct. Modern vehicles often require a scan tool to access the diagnostic trouble codes from the antilock braking system (ABS), but on some older vehicles, it is possible to use a jumper wire to initiate a diagnostic mode that flashes codes via the dashboard warning lights.

Question 6

Technician A says that a breakout box is often required to diagnose an antilock braking system. Technician B says that a breakout box requires to use of a digital multimeter. Which technician is correct?

Accepted Answer

A breakout box is a diagnostic tool used to access the signals and data on electronic control modules, including those for antilock braking systems, making Technician A correct. It also often requires the use of a digital multimeter to measure voltages, resistances, and other electrical parameters on the various pins, making Technician B correct as well.

Question 7

Technician A says that a noise or vibration may be sensed by the driver when the ABS performs a self test. Technician B says that the ABS fuse may have to be removed to erase some ABS diagnostic codes if a scan tool is not used. Which technician is correct?

Accepted Answer

Technician A is correct because it is normal for the ABS system to perform a self-test, often at the start of a drive, which can sometimes result in noticeable noise or vibration. Technician B is also correct because, in some vehicles, removing the ABS fuse or disconnecting the battery can reset the ABS system and clear certain diagnostic codes if a scan tool is not available.

Question 8

The ABS computer uses what signal characteristic from a wheel speed sensor?

Accepted Answer

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

Question 9

Most wheel speed sensors should measure how much resistance?

Accepted Answer

The answer of Most wheel speed sensors should measure how...

Question 10

Technician A says that the ABS electrohydraulic unit can be bled using bleeder screws and the manual method. Technician B says that a scan tool is often required to bleed the ABS electrohydraulic unit. Which technician is correct?

Accepted Answer

Both technicians are correct. Technician A is correct in stating that the ABS electrohydraulic unit can sometimes be bled using traditional methods with bleeder screws. Technician B is also correct because, in many modern vehicles, a scan tool is required to properly bleed the ABS system by cycling the pump and valves.

Question 11

A quick diagnostic test of wheel speed sensors (WSS) on some Bosch ABS systems is to hoist the vehicle and spin each tire individually. If the WSS is working properly ________.

Accepted Answer

The answer of A quick diagnostic test of wheel speed...

Question 12

Technician A says that the test drive is an important diagnostic step to verify customer ABS concerns. Technician B says that if the red brake warning light is on, the conventional brake system should be repaired first, before driving. Which technician is correct?

Accepted Answer

Both technicians are correct. Technician A is right because a test drive can help verify the customer's ABS concerns by replicating the issue under real-world conditions. Technician B is correct because if the red brake warning light is on, it indicates a problem with the conventional brake system, which should be addressed before driving the vehicle to ensure safety.

Question 13

How are the antilock system valves activated on a Kelsey-Hayes 4WAL system?

Accepted Answer

The antilock system valves in a Kelsey-Hayes 4WAL system are activated using pulse width modulation, which allows for precise control over the braking pressure.

Question 14

The red brake warning lamp is dimly lit on a RWD pickup with RWAL. Which is the most likely cause?

Accepted Answer

The answer of The red brake warning lamp is dimly...

Question 15

A wheel speed sensor is producing lower than expected voltage as the wheel rotates. Which of these is NOT a possible cause?

Accepted Answer

All of the listed options (incorrect air gap, debris on the sensor, and damaged or corroded electrical connector) are potential causes for a wheel speed sensor to produce lower than expected voltage.

Question 16

When observing WSS output with an oscilloscope, most sensors should produce ________.

Accepted Answer

Wheel Speed Sensors (WSS) typically produce an AC sine wave where both the amplitude and the frequency increase as the wheel speed increases.

Question 17

What reference voltage (supply voltage) is used with digital wheel speed sensors?

Accepted Answer

The answer of What reference voltage (supply voltage) is used...

Question 18

Technician A says no wheel speed sensors are adjustable. Technician B says improper tire size can cause ABS system faults. Which technician is correct?

Accepted Answer

The answer of Technician A says no wheel speed sensors...

Question 19

Technician A says interference from cell phone or CB antennae may the disrupt the ABS control unit. Technician B says many system problems can be located with a thorough visual inspection. Which technician is correct?

Accepted Answer

Both technicians are correct. Interference from cell phone or CB antennae can indeed disrupt the ABS control unit, and many system problems can indeed be located with a thorough visual inspection.

Question 20

A good wheel speed sensor should produce at least ________ with the wheel turning.

Accepted Answer

A good wheel speed sensor, which is typically a type of variable reluctance sensor, generates an AC (alternating current) signal whose voltage increases with wheel speed. A minimum of 0.1 volt AC with the wheel turning is generally considered acceptable for indicating the sensor is functioning.

Quiz 107: Abs Diagnosis and Service