Chrysler Le Baron, Dodge Dynasty, Plymouth Acclaim. Manual — part 232

The primary functions of the (CAB) are:

• (1) Detect wheel locking tendencies.

• (2) Control fluid modulation to the brakes while in
Anti-Lock mode.
• (3) Monitor the system for proper operation.

• (4) Provide communication to the DRB II while in
diagnostic mode.

The (CAB) continuously monitors the speed of each

wheel, through the signals generated at the Wheel
Speed Sensors, to determine if any wheel is begin-
ning to lock. When a wheel locking tendency is de-
tected, the (CAB) will isolate the master cylinder
from the wheel brakes. This is done by activating the
Isolation Valves. The (CAB) then commands the ap-
propriate Build or Decay valves to modulate brake
fluid pressure in some or all of the hydraulic circuits.
The fluid used for modulation comes from the booster
servo circuit. The (CAB) continues to control pres-
sure in individual hydraulic circuits until a locking
tendency is no longer present.

The (ABS) system is constantly monitored by the

(CAB) for proper operation. If the (CAB) detects a
fault, it can disable the Anti-Lock braking function.
Depending on the fault, the (CAB) will light one or
both of the brake warning lamps.

The (CAB) contains a System Diagnostic Program

which triggers the brake system warning lamps
when a system fault is detected. Faults are stored in
a diagnostic program memory. There are 19 fault
codes that may be stored in the (CAB) and displayed
through the DRB II. These fault codes will remain in
the (CAB) memory even after the ignition has been
turned off. These fault codes will remain in memory
until they are cleared with the DRB II, or automati-
cally erased from the memory after (50) ignition
switch on/off cycles.

CONTROLLER ANTI-LOCK BRAKE (INPUTS)

• Four wheel speed sensors.

• Boost pressure transducer.

• Primary pressure transducer.

• Low fluid level switch.

• Differential pressure switch.

• Parking brake switch.

• Dual function pressure switch (warning pressure
only)
• Stop lamp switch.

• Ignition switch.

• System relay voltage.

• Ground.

• Low Accumulator

CONTROLLER ANTI-LOCK BRAKE (OUTPUTS)

• Ten modulator valves-3 decay, 3 build and 4 isola-
tion.
• Red Brake warning lamp.

• Amber Anti-Lock Warning Lamp.

• System relay actuation.

• Diagnostic communication.

ABS SYSTEM DIAGNOSTIC CONNECTOR

The Bendix Anti-Lock system diagnostic connector

is located under the lower dash panel or in the area
of the fuse box (Fig. 8). The fuse box is located be-
hind the access panel that is on the bottom portion of
the dash panel, left of the steering column. The diag-
nostics connector is a blue 6 way connector.

ANTI-LOCK SYSTEM RELAYS AND WARNING
LAMPS

PUMP/MOTOR RELAY

Pump/Motor power is supplied by the Pump/Motor

Relay. The Pump/Motor relay is located inside the
Power Distribution Center (PDC). The relay coil is
energized by a ground from the Dual Function Pres-
sure Switch. See (Fig. 9) for the location of the pump/
motor relay in the (PDC).

SYSTEM RELAY

The (ABS) Modulator Valves and Anti-Lock Warn-

ing Lamp Relay are controlled through a System Re-
lay. The System relay is located on the top left inner
fender behind the headlight (Fig. 10). The system re-
lay provides power to the (CAB) for modulator valve
operation (pins 47 and 50) after the start-up cycle
when the ignition is turned on.

ANTI-LOCK WARNING LAMP RELAY

The Anti-Lock Warning Lamp is controlled by the

Yellow Light Relay. See (Fig. 10) for location behind
the left headlight. With the relay de-energized, the
lamp is lit. When the system relay is energized by

Fig. 8 A.B.S. Diagnostic Connector Location

5 - 82

ANTI-LOCK 10 BRAKE SYSTEM

Ä

the (CAB), the Anti-Lock Warning Lamp relay is en-
ergized, and the lamp is turned off. Thus, the lamp
will be lit if the (CAB) is disconnected or if a system
fault causes (ABS) function to be turned off, or if the
system relay fails open.

ANTI-LOCK WARNING LAMP OFF

System Relay (normally open) and Yellow

Light Relay (normally closed) Energized.

When the (CAB) energizes the system relay by pro-

viding 12 volts to pin 57. The voltage flow in the coil
closes the system relay. Electrical current is then
provided to pins 47 and 50 of the (CAB) to provide
power to the modulator valves. This voltage also en-
ergizes the Anti-Lock Warning Lamp Relay Switch.
This breaks the ground path to the Anti-Lock Warn-
ing Lamp and the lamp is turned off.

The (CAB) by itself, also can turn on the Anti-Lock

Warning Lamp. The (CAB) can turn on the Anti-
Lock Warning Lamp by providing a ground at pin
15.

ANTI-LOCK WARNING LAMP ON

System Relay and Anti-Lock Warning Lamp

Relay De-Energized.

When the Amber Anti-Lock Warning Lamp is on,

there is no current flow from the (CAB) at pin 57.
The system relay coil is NOT energized. No electrical
current flows to pins 47 and 50 (modulator valve
power), or to the Anti-Lock Warning Lamp relay coil.
Thus, the Anti-Lock Warning Lamp Relay is not en-
ergized. The Anti-Lock Warning Lamp is grounded
through the Anti-Lock Warning Lamp relay contacts.
The Anti-Lock Warning Lamp is illuminated.

Fig. 9 Pump/Motor

Fig. 10 ABS System Relay And Yellow Lamp Relay

Location

Ä

ANTI-LOCK 10 BRAKE SYSTEM

5 - 83

ANTI-LOCK

SYSTEM

RELAY

WIRING

SCHEMATIC

5 - 84

ANTI-LOCK 10 BRAKE SYSTEM

Ä

ABS HYDRAULIC CIRCUITS AND VALVE
OPERATION

Through the following operation descriptions and

diagrams. The function of the various hydraulic con-
trol valves in the ABS system will be described. The
fluid control valves mentioned below, control the flow
of pressurized brake fluid to the wheel brakes during
the different modes of Anti-Lock Braking.

NORMAL BRAKING

ISOLATION VALVES

Open to primary and secondary master cylinder

brake fluid supply (Fig. 11)

DECAY AND BUILD VALVES

Closed, not allowing for the build-up or release of

brake fluid supply (Fig. 11).

The brake pedal is applied. The travel of the brake

pedal closes primary, secondary and booster servo
circuits from fluid supply at the fluid reservoir.
Brake fluid from the primary and secondary circuits
flows through the open isolation valves and applies
the wheel brakes. Fluid from the booster servo cir-

cuit does not flow to the wheel brakes. The fluid flow
is blocked by the closed build valves and check
valves.

POWER ASSIST

The boost control valve shuttles between its three

positions to provide power assisted braking (Fig. 11).

ABS BRAKING-BUILD PRESSURE

ISOLATION VALVES

Closed, isolating wheel brakes from master cylin-

der primary and secondary fluid supplies and open to
booster servo circuit pressure through open build
valves (Fig. 12)

DECAY VALVES

Closed, not allowing the escape of pressurized fluid

supply from the hydraulic system (Fig. 12).

BUILD VALVES

Open, allowing booster servo circuit pressure to

flow to the wheel brakes through the isolation valves
(Fig. 12).

Fig. 11 Normal Braking - Hydraulic Control

Ä

ANTI-LOCK 10 BRAKE SYSTEM

5 - 85