1995 ACURA TL relay

'95 - 96 models:

VARIOUS

SENSORS

From

No. 4 ECU
(ECM)

(20A) FUSE

(in the under-dash

fuse/relay box)

VARIOUS

SENSORS

EVAP

TWO WAY

VALVE
EVAP

BYPASS

SOLENOID

VALVE
EVAP

THREE

WAY

VALVE
EVAP CONTROL

CANISTER

VENT SHUT VALVE
EVAP PURGE

CONTROL

SOLENOID VALVE
ECM
ECM
From

No. 4 ECU
(ECM) (15A)

FUSE (in the under-dash

fuse/relay box)

EVAP CONTROL

CANISTER
FUEL

TANK

PRESSURE

SENSOR
FUEL TANK
FUEL FILL

CAP

FUEL TANK

EVAP VALVE
FUEL TANK

'97 - 98 models:
FUEL TANK

EVAP VALVE
EVAP TWO WAY VALVE

FRESH

AIR

FUEL FILL CAP
EVAP PURGE

FLOW SWITCH
EVAP PURGE

CONTROL

SOLENOID VALVEProCarManuals.com

Troubleshooting Procedures

Checking the Diagnostic Trouble Code (DTC)

with an OBD II Scan tool or Honda PGM Tester

When the TCM senses an abnormality in the input or output systems, the indicator light in the gauge assembly will

blink. When the 16P Data Link Connector (DLC) (located behind the ashtray) is connected to the OBD II Scan Tool or Honda

PGM Tester as shown, the scan tool or tester will indicate the Diagnostic Trouble Code (DTC) when the ignition switch is

turned ON(II).

When the indicator light has been reported on, connect the OBD II Scan Tool conforming to SAE J1978 or Honda PGM

Tester to the DLC (16P) behind the ashtray. Turn the ignition switch on (II), and observe the DTC on the screen of the OBD II

Scan Tool or Honda PGM Tester. After determining the DTC, refer to the electrical system Symptom-to-Component Chart

on page 14-56 and 14-57.

NOTE: See the OBD II Scan Tool or Honda PGM Tester user's manual for specific instruction.

OBD II SCAN TOOL or

HONDA PGM TESTER

Some PGM-FI problems will also make the indicator light come on. After repairing the PGM-FI system, disconnect the

BACK UP RADIO fuse (10 A) in the under-hood fuse/relay box for more than 10 seconds to reset the TCM memory, then

retest.

NOTE: Disconnecting the BACK UP RADIO fuse also cancels the radio anti-theft code, preset stations and the clock setting.

Get the customer's code number, and make note of the radio presets before removing the fuse so you can reset them.
DATA LINK CONNECTOR (16P)ProCarManuals.com

4. Inspec t th e circui t o n th e TC M accordin g t o th e trou -
bleshootin g flowchar t wit h th e specia l tool s an d a
digita l multimete r a s shown .
How to us e th e Backprob e Se t
Connec t th e backprob e adapter s t o th e stackin g patc h
cords , an d connec t th e cord s t o a multimeter . Usin g
th e wir e insulatio n a s a guid e fo r th e contoure d ti p o f
the backprob e adapter , gentl y slid e th e ti p int o th e
connecto r fro m th e wir e sid e unti l i t come s i n contac t
with th e termina l en d o f th e wire .
BACKPROB E SE T07SAZ-001000 A
(tw o required )
BACKPROB EADAPTER
STACKIN GPATCH COR D
TCM
DIGITA L MULTIMETE R
(Commerciall y available )
KS-AHM-32-003 ,or equivalen t
TCM Rese t Procedur e
1 . Mak e sur e yo u hav e th e anti-thef t cod e fo r th e radio ,
the n writ e dow n th e frequencie s fo r th e radio' s pre -
set buttons .
2. Tur n th e ignitio n switc h OFF .
3 . Remov e th e No . 3 9 BAC K U P RADI O fus e (1 0 A )
fro m th e under-hoo d fuse/rela y bo x fo r 1 0 second s
t o rese t th e TCM .
NOTE : Th e TC M memor y canno t b e cleare d b y
usin g th e OB D II Sca n Too l o r Hond a PG M Tester ; b e
sur e to remov e th e BAC K U P RADI O fus e to rese t th e
TCM .
BACK U P RADI O
(1 0 A ) FUS E
UNDER-HOO D
FUSE/RELAYBOX
Fina l Procedur e
NOTE : Thi s procedur e mus t b e don e afte r an y trouble -
shooting.
1. Tur n th e ignitio n switc h OFF .
2 . Disconnec t th e OB D II Sca n Too l o r Hond a PG M
Teste r fro m th e Dat a Lin k Connector , o r remov e th e
specia l too l fro m th e Servic e Chec k Connector .
3. Rese t th e TCM .
4. Tur n th e ignitio n switc h O N (II) .
5 . Ente r th e anti-thef t cod e fo r th e radio , the n ente r th e
customer' s radi o statio n presets .
ProCarManuals.com

Illustrated Inde x
The accumulato r contain s high-pressur e nitroge n gas ; d o no t puncture , expos e to flame , o r attemp t t o dis -
assembl e th e accumulato r o r i t ma y explode ; sever e persona l injur y ma y result .
MODULATO R UNI T
AB S Functio n Test , pag e 19-11 2
Modulato r Functio n Check , pag e 19-11 4
Relievin g Syste m Pressure , pag e 19-11 5
Brak e Flui d Replacement , pag e 19-11 5
Removal/Installation , pag e 19-11 7
Wir e Harnes s Replacement , pag e 19-11 9
Pum p Moto r Replacement , pag e 19-11 9
Accumulato r Replacemen t an d Disposal , pag e 19-12 0
Reservoi r Replacement , pag e 19-12 0FAIL-SAF E RELAY SInspection , pag e 19-12 2
AB S CONTRO L UNI T
Replacement , pag e 19-12 1
REAR WHEE L SENSO RInspection , pag e 19-12 2
Replacement , pag e 19-12 3
ABS MOTO R RELA YInspection , pag e 19-12 2
FRON T WHEE L SENSO RInspection , pag e 19-12 2Replacement , pag e 19-12 3
ProCarManuals.com

Anti-lock Brake System (ABS)

Features/Construction

In a conventional brake system, if the brake pedal is depressed very hard, the wheels can lock before the vehicle comes to

a stop. In such a case, the stability of the vehicle is reduced if the rear wheels are locked, and maneuverability of the vehi-

cle is reduced if the front wheels are locked, creating an extremely unstable condition.

The Anti-lock Brake System (ABS) modulates the pressure of the brake fluid applied to each front caliper or both rear

calipers, thereby preventing the locking of the wheels, whenever the wheels are likely to be locked due to hard braking. It

then restores normal hydraulic pressure when there is no longer any possibility of wheel locking.

The ABS equipped on this car is compact, with its hydraulic control system incorporated into one modulator unit. It is a

3-channel anti-lock brake system that has individual control of the front wheels and common control ("select low") for the

rear wheels. "Select low" means that the rear wheel that would lock first (the one with the lowest resistance to lock-up)

determines anti-lock brake system activation for both rear wheels.

ABS CONTROL UNIT

GEAR PULSER

MASTER CYLINDER

MODULATOR UNIT

REAR WHEEL SENSOR

GEAR PULSER
FRONT WHEEL SENSOR

PART NAME

Gear pulser

Wheel sensor

ABS control unit

Modulator unit

Motor Relay

Fail-safe relay
MAJOR FUNCTION

Attached to the rotating part of the wheel and detects the wheel speed together with the

wheel sensor.

Generates pulse signal corresponding to the revolution of the gear pulser.

Controls the working of the anti-lock brake system by performing calculations based on the

signals from the individual wheel sensors and the individual switches.

• Adjusts the hydraulic pressure applied to each caliper on the basis of the signals received

from the ABS control unit.

• Pump, accumulator, solenoid valves, pressure switch and pistons are integrated in the mod-

ulator unit.

Controls the ABS pump motor's power supply according to the signal from the ABS control unit.

Cuts off the solenoid valve ground circuit when the fail-safe device is at work.ProCarManuals.com

Piston/valve:

The piston/valve assembly consists of the piston, cut valve, and sleeve. There are four piston/valve assemblies in the mod-

ulator unit to control the brake fluid pressure to each caliper. The piston/valve assemblies for the rear brakes also serve as

proportioning control valves to prevent the rear wheels from locking if the ABS malfunctions or when the ABS is not acti-

vated.

Solenoid valves:

The modulator unit opens and closes the inlet and outlet solenoid valves, and shifts the ABS high-pressure passage

according to the signals from the ABS control unit. There are three solenoid valve assemblies, each containing an inlet

and outlet valve, in the modulator unit; one for each front wheel, and one for both rear wheels. The inlet valves are nor-

mally open (open when the coil is not energized), while the outlet valves are normally closed.

MODULATOR UNIT

RESERVOIR

To ABS CONTROL

UNIT

To RIGHT-FRONT

WHEEL

To LEFT-FRONT

WHEEL

PUMP MOTOR RELAY
From MASTER

CYLINDER

PRIMARY PISTON

From MASTER

CYLINDER

SECONDARY

PISTON

To LEFT-REAR

WHEEL

To RIGHT-

REAR WHEEL
MOTOR
PUMP

PISTON/VALVE
CUT

VALVE
PISTON
SLEEVE
SOLENOID VALVES (3 SETS)

RELIEF

VALVE

ACCUMULATOR

PRESSURE

SWITCHProCarManuals.com

Anti-lock Brake System (ABS)

Features/Construction (cont'd)

Wheel sensor:

The wheel sensor is a contactless type that detects the rotating speed of a wheel. It consists of a permanent magnet and

coil. When the gear pulsers attached to the rotating parts of each wheel turn, the magnetic flux around the coil in the

wheel sensor alternates, generating voltages with frequency in proportion to wheel rotating speed. These pulses are sent

to the ABS control unit, and the ABS control unit identifies the wheel speed.

WHEEL SENSOR

COIL PERMANENT MAGNET

at HIGH SPEED

at LOW SPEED

GEAR PULSER

GEAR PULSER

ABS control unit:

The ABS control unit consists of a main function, which controls the operation of the anti-lock brake system, and sub-func-

tion, which controls the pump motor and "self-diagnosis".

For safety, the main function consists of two systems, and the ABS control unit activates the solenoid valve only when the

outputs of the two systems agree with each other.

The main function section of the ABS control unit performs calculations on the basis of the signals from each wheel

sensor, and controls the operation of the anti-lock brake system by activating the solenoid valves in the modulator unit

for each front brake and for the two rear brakes. The ABS has individual control of the front wheels and common con-

trol ("Select low") for the rear wheels. "Select low" means that the rear wheel that would lock first (the one with the

lowest resistance to lock-up) determines the ABS activation for both rear wheels.

The sub-function section has the fail-safe function that monitors the system operation by inputting the brake switch,

parking brake switch and pressure switch signals, and stops the anti-lock brake system when it detects an abnormality

in the system. It also has a self-diagnosis function and the pump motor control function.

WHEEL SENSORS
ABS CONTROL UNIT

RIGHT-FRONT WHEEL

LEFT-FRONT WHEEL

RIGHT-REAR WHEEL

LEFT-REAR WHEEL

BRAKE SWITCH

PARKING BRAKE SWITCH
MAIN FUNCTION

• BASIC ABS

FUNCTION CONTROL

SUB-FUNCTION

• SELF-DIAGNOSIS FUNCTION

• FAIL-SAFE FUNCTION

• PUMP MOTOR CONTROL

PRESSURE SWITCH

PUMP MOTOR RELAY
MODULATOR UNIT

SOLENOID

SOLENOID

SOLENOID

FRONT FAIL - SAFE RELAY

REAR FAIL - SAFE RELAY

PUMP MOTORProCarManuals.com

Pump motor control:

The ABS control unit monitors the brake fluid pressure in the accumulator by the pressure switch ON/OFF signals. The

ABS control unit turns the pump on when the pressure in the accumulator drops, and stops the pump when the pressure

rises to the specified value.

If the pressure does not reach the specified value after the motor has operated continuously for a specified period, the

ABS control unit stops the motor and activates the ABS indicator light.

Self-diagnosis function:

The self-diagnosis function, provided in the sub-function of the ABS control unit, monitors the main system functions by

constantly transmitting the data between the two Central Processing Units (CPUs). When an abnormality is detected, the

ABS control unit turns the ABS indicator light on and stops the ABS, although the basic brake system continues to operate

normally.

When the ABS control unit detects an abnormality with the ABS and turns the ABS indicator light on, the diagnostic trou-

ble code (DTC), which shows the problem part or unit, is recorded in the control unit. The DTC can be read by the blinking

frequency of the ABS indicator light.

Fail-safe function:

When an abnormality is detected in the ABS control sys-

tem self-diagnosis, the solenoid operations are suspend-

ed by turning off the two fail-safe relays. This discon-

nects the ground circuits of all the solenoid valves to

prevent ABS operation.

Under these conditions, the braking system functions

just as an ordinary one.

Fail-safe relay:

The fail-safe relay's terminal side contact is normally

open. When there is continuity at the relay coil, the fail-

safe relay is closed, thereby connecting the ground cir-

cuit to the solenoid valve.

ABS indicator light:
SOLENOID VALVE

BAT

REAR FAIL-SAFE RELAY

FRONT FAIL-SAFE RELAY

The ABS control unit turns the ABS indicator light on when one or more of the following abnormalities are detected. This

is only a partial list.

When the operating time of the motor in the power unit exceeds the specified period.

When vehicle running time exceeds 30 seconds without releasing the parking brake.

When absence of speed signals from any of the four wheel sensor is detected.

When the activation time of all solenoids exceeds a given time, or an open circuit is detected in the solenoid system.

When solenoid output is not detected in the simulated ABS operation when the engine is started or the vehicle is driven.

To check the indicator light bulb, the light is activated when the ignition switch is first turned on. The light goes off after

the engine is started if there is no abnormality in the system.
ABS CONTROL UNITProCarManuals.com