Systems Repair Worksheet
ABS & Traction Control
Chapter 51
Pages 1506-1534
Name_______________________
59 Points
Due Date________
1. ABS systems use an __________________/______________ pumping of the brakes to control
straight-line stopping under panic conditions. (ABS is very fast, up top 15 x/second, & very precise)
2. Pressure ____________________ is the term used to describe the quick apply & release of brake
system pressure by the antilock brake system. (preventing lock-up leads to better maneuverability & stability)
3. _______ ______ is the difference between the actual speed of the vehicle and the speed of the tire’s
tread as it rotates on the pavement. With ABS, the target slip rate is 10% to 30%
4. It’s the traction of the _______ that actually stops the vehicle. ABS adjusts slip rate at each tire.
5. If the driver pumps the brakes while stopping, this prevents ABS from activating. True or False
6. When ABS is activated, a small ________ followed by rapid pedal __________________ will
continue until the vehicle either comes to a stop or the ABS turns off.
7. There are both ___________________ and _______________________/____________________
components in each ABS system. These are also used for traction control system operation.
8. The nitrogen-charged __________________ is used to store the hydraulic fluid used to maintain
high ABS pressure. It may also be used to store residual pressure for power-assisted braking.
9. The control valve assembly may be an _______________ part of the master cylinder assembly or
may be mounted externally away from the master cylinder (non-integral).
10. The _____________ pump, an assembly of an electric motor & pump, provides pressurized fluid.
11. The booster/ master cylinder assembly, sometimes referred to as the hydraulic __________ unit,
contains the valves and pistons needed to modulate hydraulic pressure.
12. Fluid ____________________ are different than pressure accumulators. They are used to
temporarily store brake fluid removed from the wheel brake units during an ABS cycle.
13. The ________ valve is a two-position valve that is only open during the ABS mode.
14. The __________________ unit is made up of solenoid valves used to either, increase, decrease, or
maintain hydraulic pressure to the individual wheel units. The valve block may also contain solenoids.
15. There are two solenoid valves known as wheel ___________ valves used to control each channel.
16. The ABS control module relies on input from the __________ speed sensors and feedback from
the hydraulic unit to determine if ABS is operating properly or which mode of ABS is required.
17. The brake __________ position sensor (BPP) determines pedal travel & signals the ECU that an
ABS event is taking place. This along with wheel speed sensor input causes a system reaction.
18. ABS systems have their own _______ for faults which are accessed through the OBDII DLC.
19. The __________-colored warning lamp (ABS MIL) illuminates vehicle startup during the ABS
system self check as well as when an ABS DTC (Diagnostic Trouble Code) is stored.
20. A _____________ acceleration sensor is used on vehicles with ABS & stability control.
21. A ______________- switch automatically controls the ground side of the pump relay energizing
and de-energizing the pump to maintain proper accumulator pressure.
22. The ABS system has __________ that complete the high current circuits for the pump motor.
23. The ______________ ring (reluctor or toner ring) of the wheel speed sensing device can be
located on an axle shaft, differential gear, or a wheel hub.
24. The wheel speed sensor (coil & permanent magnet) & toner ring generate an ____ voltage signal.
25. The electronic circuit & wiring of ABS is tied into the vehicle’s CAN ______________. This is a
high speed way of transferring information between computers on a serial data bus. (Multiplexing)
26. The ABS control unit operates _______________ / ______ valves in the hydraulic control unit
that block off or isolate the master cylinder from certain brakes. These are corner specific valves.
27. Manufacturers have unique ways of accomplishing ABS operation. _____________ systems with
conventional power-assisted master cylinders & separate ABS hydraulic control units are typical.
28. ____________ is the name given to a hydraulic circuit to the brakes. (ABS can be 1,2,3, or 4 channel)
29. Light trucks and some SUV’s use 1-channel ABS on just the ________ brakes. (RWAL or RABS)
30. A diagonally split system may us a ____-channel system that modulates opposite corners.
31. A ____-channel system will individually control each front brake but use an RWAL/RABS system.
32. The most effective and most commonly available ABS is the ____-channel system with a sensor
for each wheel. Normal braking is done by a conventional vacuum power-assist system.
33. Based on input from wheel speed sensors, the ABS control module calculates the ________ rate
of the wheels and then controls the brake fluid pressure to reach the target slip rate.
34. __________ _________ sensors are variable-reluctance sensors or permanent magnet generators.
35. As wheel speed changes, sensor AC ______________ & _______________ change in accordance.
36. Hydraulic control in the ABS modulator assembly has 3 modes of operation:
1) Pressure _____________ [dump], 2) Pressure _____________ [hold], 3) Pressure _________________ [build]
37. Automatic __________ control (ATC) systems apply the brakes when a drive wheel attempts to
spin and lose traction. The goal is still controlling wheel slip rate.
38. ______ controls negative wheel slip and ______ controls positive wheel spin.
39. The EBCM and the PCM will work together to reduce engine ____________ during traction
control mode. This can be accomplished through retarding spark timing, closing the throttle,
limiting injctor pulse width, increasing EGR flow, and up-shifting the transmission.
40. When ATC is actively controlling wheel spin, a __________ lamp is illuminated on the cluster.
41. Some traction control systems have a manual ______-______ switch. The amber-colored traction
control system lamp on the instrument cluster will then be illuminated.
42. Electronic _________________ Control (ESC) helps prevent skids, swerves, and rollovers.
43. _______________ is a condition where the vehicle is slow to respond to steering changes. (plow)
44. _______________ is a condition when the rear wheels try to swing around or fishtail. (loose)
45. ______ is defined as the natural tendency of a vehicle to rotate on its vertical axis.
46. ______ is the tendency of a vehicle to rotate on its horizontal axis. Pitch is forward-rearward dip.
47. A vibration-type _____________ senses understeer & oversteer signaling the need to correct yaw.
48. There are many ABS, ATC, and ESC ____________ Procedures & OEM Service Precautions!
49. An important thing to remember about ABS service is to relieve ___________________ pressure
before performing any hydraulic system service. 28,000 psi of pressure may be present!
50. A common method of depressurization is to ______ the pedal 25 times with the ignition key off.
51. All ABS systems have some sort of _______-________,activated each time the ignition switch
is turned on (KOEO).
52. A solid (not-flashing) ABS lamp indicates a __________ has been detected and ABS is inhibited
although normal power-assisted braking is still present. A flashing lamp means repair ASAP!
53. ABS fault codes cannot be ____________ until all faults have been corrected and the vehicle has
been driven for a manufacturer-specified rate and distance.
54. Many of the components in an ABS system are serviced by ________________ only.
55. Brake ______________ is one area of service that will vary by manufacturer and system design.
56. The auto brake system continues to evolve with things like ___________ calipers, brake-by-wire,
electronic wedge brakes, rain-sensing brakes that apply to self-dry and hill hold features.