1987 MAZDA 626 Workshop Manual

ANTI-LOCK BRAKE SYSTEM (ABS) 1 1
TROUBLESHOOTING
Precaution
Conditions that are not malfunctions
1. It may happen that vibration is felt in the steering wheel, body, and/or brake pedal when the ABS
is functioning; such vibration is simply an indication that the system is functioning.
2. Sound of the pump motor operating, accumulator pressure being released, or the relay operating
may be heard from the engine compartment when the engine is started as the system is being auto-
matically checked.
3. The ABS pump motor may be automatically activated even though the ABS is not operating.
4. The ABS warning light may illuminate under any of the following conditions:
• When the vehicle is traveling on snow or ice with the parking brake activated or a brake dragging
at one wheel.
• When different-sized tires are used.
• When tires of different gripping performance are used.
• When (while the vehicle is jacked up or stuck) only the front wheels are spun for 20 seconds or more.
• When there is insufficient battery voltage.
Note
Under the above conditions, the warning light will not illuminate a second time when the
ignition is switched OFF then back ON, and there will be no memory entry to the control
unit of a problem.
Troubleshooting notes
The ABS is composed of electrical components, mechanical components (hydraulic unit), and the com-
ponents of the standard brake system.
Fundamentally, malfunction of the ABS electrical or mechanical components is judged by the self-
diagnosis function within the ABS control unit. And malfunctions are indicated by the warning light
in the instrument panel.
The location
of
a malfunction is indicated by the technician switching the system to the diagnosis-indication
mode.
The self-diagnosis and indication functions must be used when malfunctions of the ABS are being
diagnosed.
76G11X-091
11—73

1 1 ANTI-LOCK BRAKE SYSTEM (ABS)
Troubleshooting Main Flow Chart
Check that the ABS warning light operates.

• Turn ignition switch OFF
to
ON, and check that ABS warning light illuminates constantly.

Flashing (Past failure)
OK
Check the ABS for failure.
• Start engine, and observe flashing
of
warning light.
Does not
illuminate
constantly
Warning light Possible cause
Does
not il-

luminate
at all

Refer
to
page 11—86.

ON
Alternator
L
ter-minal output Wiring harness (ALT-control unit) Control unit

OFF
1 sec

Alternator
L
ter-minal output Wiring harness (ALT-control unit) Control unit

ON
Relay box wiring harness (warning light-control unit) Control unit

OFF
1 sec

Relay box wiring harness (warning light-control unit) Control unit

No illumination
(Not diagnosed)
Illuminates constantly
(Present failure)
ABS is usually operating cor-rectly.
Consult table below when ABS failure
is
still suspected.
System Possible cause
ABS Brake light switch
Both rear wheel speed sensors
Control unit Proportioning
valve
in hy-
draulic unit
Other than Refer
to

ABS troubleshoot-ing guide
on

page 11—5.

Repair failures with flow
chart. (Refer to page
11—76.)
76G11X-054
11-74

ANTI-LOCK BRAKE SYSTEM (ABS) 1 1
Diagnosis Table
Note
Flashing of the warning light shows past failure, and its illumination shows present failure.
Diagnosis indication Possible failure Flow chart
No. Warning light Voltmeter Possible failure Flow chart
No.
ON
n
i2vn
OV

Hydraulic unit Harness
Right front wheel speed
sensor ABS-1
ON
n nn
Hydraulic unit Harness Left front wheel speed sensor ABS-2

OFF

Hydraulic unit Harness Left front wheel speed sensor ABS-2

OFF
nnn

Hydraulic unit Harness
Rear wheel speed sensor ABS-3

n
nnnn
Right front sensor rotor ABS-4

n
nnnnn
Left front sensor rotor ABS-5

JLilTUITLTL
Right rear sensor rotor ABS-6

jirLruiJum
Left rear sensor rotor ABS-7

J n
Hydraulic unit Harness
Control unit connector (11-pin)
ABS-8

nnnn

Hydraulic unit Harness
Control unit connector (11-pin)
ABS-8

J nn

Relay box
Hydraulic unit
Harness
ABS-9

jumruiTL

Relay box
Hydraulic unit
Harness
ABS-10

j nnn
Relay box
Hydraulic unit
Harness
ABS-11

jinnjuuL

Relay box
Hydraulic unit
Harness ABS-12

j nnnn

Relay box
Hydraulic unit
Harness
ABS-13

jiruuirirL

Relay box
Hydraulic unit
Harness
ABS-14

j nnnnn
Hydraulic unit Harness Control unit
ABS-15

juuuiruL

Hydraulic unit Harness Control unit ABS-16

j JinjiruifL.
Control unit
ABS-17

jiruinjiri—
JinjiruifL.
Control unit
ABS-18

j
No signal; failure condi-tions not stored
in
memory
Control unit Control unit connector (17-pin) Battery capacity Alternator output voltage Wiring harness (warning light-control unit-check connector)
Inspect, and repair or replace as necessary
j
No signal; failure condi-tions not stored
in
memory
No problem When warning light does
not
illuminate with engine running and
no
jumper wire

76G11X092
11-75

1 1 ANTI-LOCK BRAKE SYSTEM (ABS)
Flow Chart (Refer to Wiring Diagram, Page 11—72.)
ABS-1
Possible failure
Right front wheel speed sensor, Harness, Hydraulic unit
Disconnect Q-01 (11-pin) connec-tor. Check continuity
at
harness side.
Q-01 (11-pin)
I
Continuity
Y (2C) Ground No

OK

Measure resistance
at
harness side.
Q-01 (11-pin) Resistance
Y (2C)
i 0
(2D) 800—1200
Q
OK
NG
Repair harness.

(Control unit — Right front sensor)
NG

Disconnect Q-03. Measure resistance
at
sensor.
Q-03 Resistance
Y
[ O
800—1200 Q

NG
Replace right front wheel speed sensor.

OK
Repair harness.

(Control unit — Right front sensor)

Check followings*
• Clearance between sensor and rotor standard: 0.3—1.1
mm
(0.012-0.043
in)
• Objects sticking
to
sensor
or
rotor
• Damaged sensor
or
rotor
• Sensor installation Tightening torque: 16-23 N-m (1.6-2.3 m-kg, 12—17 ft-lb)

OK

Connect Q-01 (11-pin) connector. Jump GB
to B at
Q-07 connector. Start engine. Check that warning light stays ON. Drive vehicle and check that warning light flashes (0.25 sec ON OFF)
at 15
km/h
(9
mph).

NG
Repair
or
replace
as
necessary
* All conditions can
be
verified
as
follows,
if an AC
voltmeter
is
available. 1. Jack
up
vehicle. 2. Measure sensor voltage while rotating right front wheel
one
revolution
per
second.
Q-01 (11-Din) Voltage (AC)
Y (2C) O (2D) More than 0.25V

NG
Check Q-01 connector,
or
Replace control unit.

OK

Replace hydraulic unit.

76G11X-055
11—76

ANTI-LOCK BRAKE SYSTEM (ABS) 1 1
ABS-2
Possible failure
Left front wheel speed sensor, Harness, Hydraulic unit
Disconnect
Q-01
(11-pin)
con-
nector.
Check continuity
at
harness side.
Q-01 (11-pin) Continuity
W (2A) Ground No

OK

Measure side.
Q-01 (11-pin) Resistance
W (2A) R (2B) 800-1200
fl
OK

Connect Q-01 (11-pin) connector. Jump GB
to B
at (Q-07) connector. Start engine.
Check that warning light stays ON. Drive vehicle and check that warn-ing light flashes (0.25 sec ON OFF) at
15
km/h
(9
mph).

NG
Repair harness (Control unit
—
Left front sensor)
resistance
at
harness

NG

Disconnect Q-02 Measure resistance
at
sensor.
Q-02 Resistance
W
| R
800-1200
0
OK

Check followings*
• Clearance between sensor and rotor standard: 0.3—1.1
mm
(0.012-0.043
in)

• Objects sticking
to
sensor
or
rotor • Damaged sensor
or
rotor
• Sensor installation Tightening torque: 16-23 N m
(1.6—2.3 m-kg, 12-17 ft-lb)

NG
OK
NG
Repair
or
replace
as
necessary

NG
Check Q-01 connector,
or
Replace control unit.

OK

Replace hydraulic unit.
Replace left front wheel speed
sensor.
Repair harness.
(Control unit
—
Left front sensor)
"All conditions can
be
verified
as
follows,
if an AC
voltmeter
is
available. 1. Jack
up
vehicle. 2. Measure sensor voltage while rotating left front wheel
one
revolution
per
second.
Q-01 (11-pin) Voltage (AC)
W (2 A)
|
R (2B) More than
0
25V

86U11X-146
11-77