Troubleshooting guide

ManualsBrandsBENDIX ManualsComputer equipmentEC-60 ABS-ATC ESP CONTROLLERS ADV

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Section 6: Antilock Braking Systems

See section 12 for other system schematics.

ABS Components

Typical ABS components (for trucks and tractors) are:

• Wheel speed sensors (such as the Bendix

WS-24

™

wheel speed sensors shown on this page). Each

sensor is installed with a Bendix Sensor Clamping

Sleeve. Vehicles have an exciter ring (or “tone ring”)

as part of the wheel assembly, and as the wheel turns,

the teeth of the exciter ring pass the wheel speed

sensor, generating an alternating current (AC) signal.

The signal varies in voltage and frequency as the wheel

speed changes. The ECU receives the AC signal and

can then monitor how fast the wheel is turning.

• Pressure Modulator Valves (PMV) (such as the

Bendix

M-32

™

or M-32QR

™

pressure modulator

valves - shown on this page). PMVs use solenoids

with the ability to apply, hold, or release the air

pressure being delivered to the brakes to optimize

brake performance. Four, ﬁ ve, or six of these valves

may be used depending on the ECU model and vehicle

conﬁ guration.

Bendix

Antilock Braking Systems (ABS) use wheel

speed sensors, ABS pressure modulator valves, and an

Electronic Control Unit (ECU) to control either four or

six wheels of a vehicle. Bendix ECUs are able to optimize

slip between the tire and the road surface by monitoring

individual wheel turning motion during braking, and

adjust (or pulse) the brake pressure at the wheel end.

When excessive wheel slip — or wheel lock-up — is

detected, the ECU will activate the Pressure Modulator

Valves similar to a driver pumping the brakes. The ECU,

however, is able to pump the brakes on individual wheels

(or pairs of wheels), independently, and with greater

speed and accuracy than a driver.

In addition to the ABS function, premium models of the

ECUs provide an Automatic Traction Control (ATC)

feature. Bendix ATC can improve vehicle traction during

acceleration, and lateral stability while driving through

curves. ATC utilizes Engine Torque Limiting where

the ECU communicates with the engine’s controller and/

or Differential Braking where individual wheel brake

applications are used to improve vehicle traction.

Premium ECUs have a drag torque control feature which

reduces driven-axle wheel slip (due to driveline inertia)

by communicating with the engine’s controller and

increasing the engine torque.

Bendix

ESP

Electronic Stability Program - Full

Stability System

The ESP

full stability functionality of the Bendix

Advanced ABS system responds to a wide range of

low- to high-friction surface scenarios including rollover,

jackknife and loss-of-control. It is the recommended

system for all power vehicles and especially critical for

tractors pulling trailers. In the case of vehicle slide (over-

steer or under-steer situations), the system will remove

the throttle and then brake one or more of the “four

corners of vehicle” (in addition to potentially braking the

trailer), thus applying a counter-force to better align the

vehicle with an appropriate path of travel. For example, in

an over-steer situation, the system applies the “outside”

front brake; while in an under-steer situation, the “inside”

rear brake is applied.

In the case of a potential roll event, the system will

reduce the throttle and quickly apply the brakes to slow

the vehicle combination below the threshold.

Trailer ABS

See the section beginning on page 41 for more information

on trailer ABS systems and components.

Antilock Braking Systems: Components

90° Speed

Sensors

Straight Speed

Sensors

Sensor

Clamping

Sleeve

Bendix

WS-24

™

Wheel Speed Sensors

Delivery

Supply

Exhaust

Electrical

Connector

Bendix

M-32QR

™

Modulator

Bendix

M-32

™

Modulator

Supply