ACURA TL 1995 Service Repair Manual

Component Locations

RIGHT-REAR WHEEL SENSOR

SERVICE CHECK CONNECTOR (2P)

ABS CONTROL UNIT
RIGHT-REAR WHEEL

SENSOR CONNECTOR

UNDER-DASH RELAY BOX

RIGHT-FRONT WHEEL

SENSOR CONNECTOR

UNDER-HOOD

FUSE/RELAY BOX

LEFT-REAR

WHEEL SENSOR

MODULATOR UNIT

UNDER-HOOD ABS

FUSE/RELAY BOX
LEFT-REAR WHEEL

SENSOR CONNECTOR

PARKING BRAKE SWITCH

UNDER-DASH FUSE/RELAY BOX

RIGHT-FRONT

WHEEL SENSOR

LEFT-FRONT WHEEL SENSOR
LEFT-FRONT WHEEL

SENSOR CONNECTORProCarManuals.com

ABS INDICATOR LIGHT
BATTERY

(100 A) FUSE

STOP/ HORN

(20 A) FUSE
IG (50 A) FUSE

UNDER-DASH FUSE/RELAY BOX

UNDER-HOOD ABS FUSE/RELAY BOX

HEATER

CONTROL RELAY

(7.5 A) FUSE

BACK-UP LIGHTS/

METER LIGHTS

(SUN ROOF)

(10 A) FUSE
ECU (ECM)/

CRUISE CONTROL/

EAT ECU

(15 A) FUSE
ABS MOTOR (30 A) FUSE

ABS B1 (20 A) FUSE

UNDER-DASH RELAY BOX
ABS PUMP MOTOR RELAY

ABS UNIT (7.5 A) FUSE

FAIL-SAFE RELAYProCarManuals.com

Anti-lock Brak e Syste m (ABS )
Features/Constructio n
When th e brak e peda l i s depresse d durin g driving , th e wheel s ca n loc k befor e th e vehicl e come s t o a stop . I n suc h a case ,
th e maneuverabilit y o f th e vehicl e i s reduce d i f th e fron t wheel s ar e locked , an d th e stabilit y o f th e vehicl e i s reduce d i f th e
rea r wheel s ar e locked , creatin g a n extremel y unstabl e condition . Th e AB S precisel y control s th e sli p rat e o f th e wheel s t o
ensur e th e gri p forc e o f th e tires , an d i t thereb y ensure s th e
maneuverability an d stabilit y o f th e vehicle .
Judgin g th e vehicl e speed , th e AB S calculate s th e sli p rat e o f th e wheel s base d o n th e vehicl e spee d an d th e whee l speed ,
then it control s th e brak e flui d pressur e to attai n th e targe t sli p rate .
Grip Forc e o f Tir e an d Roa d Surfac e Sli
p Rat e
COEFFICIEN T O FFRICTIO N
TARGET SLI P RAT E
SLI P RAT E ROTATIONA
L
DIRECTIO N
RADIALDIRECTIO NOF TH EROTATIONA L
DIRECTIO N
BRAKINGSTART POIN T STO
P POIN T
SOLENOI D
ProCarManuals.com

Operation

ABS Control Unit

Main Control

The ABS control unit detects the wheel speed based on the wheel sensor signal it received, then it calculates the vehicle

speed based on the detected wheel speed. The control unit detects the vehicle speed during deceleration based on the

rate of deceleration.

The ABS control unit calculates the slip rate of each wheel, and it transmits the control signal to the modulator unit

solenoid valve when the slip rate is high.

The pressure reduction control is a three-mode system, that is pressure reduction, pressure retaining and pressure intensi-

fying modes.

ABS CONTROL UNIT

Self-diagnosis Function

The ABS control unit is equipped with a main CPU and a sub CPU, and the CPUs check each other.

The CPUs check the circuit of the system.

The
self-diagnosis
can be
classified
into
two
categories.

Initial diagnosis

Regular diagnosis

On-board Diagnosis Function

The ABS control unit is connected to the data link connector.

The ABS system can be diagnosed with the Honda PGM Tester.ProCarManuals.com

Anti-lock Brake System (ABS)

Operation (cont'd)

ABS Modulator

The ABS modulator consists of the inlet solenoid valve, outlet solenoid valve, reservoir, pump, pump motor and the

damping chamber.

The modulator reduces the caliper fluid pressure directly. It is a circulating-type modulator because the brake fluid circulates

through the caliper, reservoir and the master cylinder.

The hydraulic control has three modes: pressure reduction, pressure retaining and pressure intensifying.

The hydraulic circuit is the independent four channel-type, one channel for each wheel.

PUMP

MOTOR

Pressure intensifying mode: Inlet valve open, outlet valve closed

Master cylinder fluid is pumped out to the caliper.

Pressure retaining mode: Inlet valve closed, outlet valve closed

Caliper fluid is retained by the inlet valve and outlet valve.

Pressure reduction mode: Inlet valve closed, outlet valve open

Caliper fluid flows through the outlet valve to the reservoir.

Motor operation mode: When starting the pressure reduction mode, the pump motor is ON.

When stopping ABS operation, the pump motor is OFF.

The reservoir fluid is pumped out by the pump, through the damping chamber, to the master

cylinder.
SOLENOID VALVEProCarManuals.com

Wheel Speed and Modulator Control

When the wheel speed drops sharply below the vehicle speed, the inlet valve closes to retain the caliper fluid pressure.

When the wheel speed drops further, the outlet valve opens momentarily to reduce the caliper fluid pressure. The pump

motor starts at this time.

As the wheel speed is restored, the inlet valve opens momentarily to increase the caliper fluid pressure.

Wheel Sensor

The wheel sensors are the magnetic contactless type.

As the gear pulser teeth rotate past the wheel sensor's magnetic coil, AC current is generated. The AC frequency changes

in accordance with the wheel speed. The ABS control unit detects the wheel sensor signal frequency and thereby detects

the wheel speed.

There are four wheel sensors, one for each wheel.

The gear pulser has 50 teeth.

GEAR PULSER

WHEEL SENSORProCarManuals.com

ABS Control Unit Terminal Arrangement

ABS CONTROL UNIT 22P CONNECTOR

Wire side of female terminals

VB: Battery VoltageProCarManuals.com

VB: Battery VoltageProCarManuals.com

ABS Control Unit Terminal Arrangement

ABS CONTROL UNIT 12P CONNECTOR

Wire side of female terminals

VB: Battery VoltageProCarManuals.com

Troubleshooting Precautions

ABS Indicator Light

1. If the system is OK, the ABS indicator light goes off two seconds after turning the ignition switch ON (II) without start-

ing the engine. After starting the engine, the ABS indicator light comes on again and goes off after two seconds. This

occurs because the ABS control unit is activated by the IG2 power source.

2. The ABS indicator light comes on when the ABS control unit detects a problem in the system. However, even though

the system is normal, the ABS indicator light comes on, too, under the following conditions. To determine the actual

cause of problem, question the customer about the problem, talking the following conditions into consideration.

Only drive wheels rotate

One wheel stuck of drive wheels

Vehicle spin

ABS operate condition continue for long time

Signal disturbance

3. When a problem is detected and the ABS indicator light comes on, there are cases when the indicator light stays on

until the ignition switch is turned OFF, and cases when the indicator light goes off automatically when the system

returns normal. For the DTC 61 and 62, the indicator light goes off automatically when the system returns normal. For

all other codes, the indicator light stays on until the ignition switch is turned OFF.

4. For DTCs 12, 14, 16, 18, 21, 22, 23, 24, 51, 52 and 53, the indicator light goes off when the vehicle is driven again and

the signals are OK after the ignition switch is turned from OFF to ON (II). However, if the DTC is erased, the CPU is

reset and the indicator light goes off right after the engine is started if the signals are OK.

Diagnostic Trouble Code (DTC)

1. The DTC is not memorized if the CPU cannot be activated or the CPU fails and the indicator light comes on.

2. The memory can hold any number of DTCs. However, when the same DTC is detected more than once, the later one

is written over the old one. Therefore, when the same problem is detected repeatedly, it is memorized as one DTC.

3. The DTCs are indicated in the order of ascending number, not in the order they occur.

4. The DTCs are memorized in the EEPROM (non-volatile memory). Therefore, the memorized DTCs cannot be canceled

by disconnecting the battery. Perform the specified procedures to erase the DTCs.

Self-diagnosis

1. The self-diagnosis can be classified into two categories.

Initial diagnosis: Performed right after the engine starts and until the ABS indicator light goes off.

Regular diagnosis: Performed right after the initial diagnosis until the ignition switch is turned OFF.

2. When a problem is detected by self-diagnosis, the system

Turns the ABS indicator light ON

Memorizes the DTC

Turns the fail-safe relay OFF

Stops ABS controlProCarManuals.com