Workbook, Heavy Duty Truck Systems, 6E
Chapter Thirty – Answer Key
1. What happens if an ABS ceases to function?
2. Which type of sensor do pneumatic ABS brakes use to signal wheel speed data to the
electronic control unit (ECU)?
3. When an ABS is first powered up, what causes the clicking noise?
4. Technician A says that in a combination tractor/semi-trailer rig, both equipped with ABS,
the ECU on the tractor controls ABS on the trailer. Technician B says that today all new
highway trucks and trailers are required to have ABS. Who is correct?
5. In a tandem drive tractor with 4S/4M air ABS, which of the following would be true?
6. Which of the following accounts for the lower modulation rates of air brake ABS when
compared with hydraulic ABS?
7. What type of voltage signal is produced by an ABS wheel speed sensor?
8. How many teeth does a current truck ABS wheel speed pulse (chopper) wheel have?
9. What is the lowest threshold voltage value at which ABS will cease to function properly?
10. When an EBS is used on a truck air brake system, which of the following circuits is
replaced by an electronic circuit?