MITSUBISHI GALANT 1989 Service Repair Manual

35-20SERVICE BRAKES - Anti-lock Braking System Troubleshooting
METHOD OF CLEARING DIAGNOSTIC
TROUBLE CODE MEMORY
Caution
l When servicing is finished, clear the diag-
nostic trouble code memory.
Diagnostic trouble codes cannot be cleared from
memory when the ABS ECU system in fail safe.
Proceed to diagnosis and repair.
(1) Clear memory using scan tool.
(For details, refer to the scan tool instruction
manual.)
(2) After clearing, recheck the diagnostic trouble
codes, and check that memory is cleared.
Actuator test specifications ACTUATOR TEST FUNCTION
The actuator can be forcibly driven in the following
way by using the scan tool.
NOTE
lThe actuator test cannot be carried out when
the ABS ECU system is fail safe.
lWhen using forced drive using the scan tool, the
vehicle must be stopped.
lDuring forced drive using the scan tool, forced
drive operation is stopped when any wheel
speed reaches 10 km/h (6 mph).
No.ScGc;r$ol displayDrive solenoidvalve and motor
01
02
FR VALVE A
FL VALVE ASolenoid valve andpump motor foreach HU corres-ponding channel.
I
03REAR VALVE A
Solenoid valve and
04FR VALVE Mpump motor foreach HU corres-ponding channel.
05FL VALVE M
I
06REAR VALVE M
Drive pattern
Not used
Pressure
increaseI I
Solenoid Pressurevalve
Pump ONIms! 3s I 3sImotorOFFIStart of forced drive
I
End of forced drive

SERVICE BRAKES - Anti-lock Braking System Troubleshooting35-21
A ABS warning light does not light at all.
[Explanation]
When it does not light up at all, there is a strong
possibility that there is trouble with ABS warning
light or with power to the light.
[Hint]
If other warning lights do not light up either, fuse is
probably blown.
MAIN FUSIBLE
LINK @IGNITIONSWITCH (IG2)IGNITIONSWITCH (IGl)
Ea
1
0 U
, ,8--1I
CL
, VALVE
fI*I1 RELAY 1 Ii 1,
M
i 10
z 13-
--3z2-&
rc11_ 3
t”71
_----
a-II
2
dt II
zz
c:
35 126J.27ABS ECU
1
GND GND GNDv v v
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14A0085

35-22SERVICE BRAKES- Anti-lock Braking System Troubleshooting
- N

o
With the ignition key in the “ON” posi-
Check fuse No. 9. If it is
tion. do other warning lights illuminate?
* blown, correct the cause of
the blown fuse and thenreplace the fuse.
I
Yes
Turn the ignition switch OFF and check.
4II., III,
Is the ABS warning light normal? (CheckNo cABS warning light bulb Replace ABS warning
for burned bulb.)burned.* light bulb.
I
Yes
NoThe harness between the
combination meter from
* fuse No. 9 is broken.
1
Repair harness.I
Circuit in combination metercRepair or replace com-
is broken. bination meter.
Yes
Is there continuity between terminals No.NoMalfunction of combination Repair or replace combi-
;,d”,l” No. 17 on the combination meter -meter
nation meter
Yes
Are instrument panel wiring harness, _
Noc Connect connectors firmly.
engine compartment wiring harness,
body wiring harness and ABS wiring
harness connectors connected properly? (Check for pins pulled out or
bent, repair as needed.)
Yes
Broken wire in ECU, valve relay or both
drive circuits. Check and repair both
circuits.
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SERVICE BRAKES - Anti-lock Braking System Troubleshooting35-23
the ignition key in the
position, remove the ECU connector
Does the voltage between ECU harness
No r Broken wire between ABS .
connector terminal No.25
and ground
indicate battery voltage? warning light and ECU.Repair harness.
Yes Replace ABS ECU.
(Remove valve relay and check.
>
Valve relay malfunction Replace valve relay.I
Yes
/Install
the valve relay and,
\
ignition key in the “ON
”
remove the HU connector and
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Does voltage between the HU harnessNo * Broken harness wire be- -Repair harness.
connetor terminal No.8 and ground indi-
tween ABS warning lightIcate
battery voltage? and HU
I
I Yes
Is there continuity between HU harness
No - Broken harness wire be-Repair harness.
connector terminal No.9
and ground? tween HU and ground
I
‘- N
o
Is there continuity between terminals No.
8 and No. 9 on the HU side connector?
I
- Repair harness or replaceHU.
YesConnector connection mal-
function
NOTEWhen inspecting the parts marked with l ,take care to the diode polarity. (Refer to the circuit diagram on P.35-21.)

35-24
SERVICE BRAKES - Anti-lock Braking System Troubleshooting
B ABS warning light illuminated after the engine is started and remains o\
n.
[Explanation]
This is the symptom when the ABS ECU does not
power up due to broken ECU power circuit, etc.,
when the fail safe function operates and isolates the
system or when the warning light drive circuit is
short circuited.
[Hint]
Check the on-board diagnostic output and if there is
no output voltage or if the scan tool and ABS ECU
cannot communicate, there is a good possibilit
y
that power is not flowing to the ECU.
Caution
l If there is no output of diagnostic trouble
codes, there is a good possibility that the
fail safe is functioning.
J/B
IGNITION
%FH
z
&7
i
CD10A
728
Is there on-board diagnostic No )output? (Is there communi-cation with scan tool?) CONTINUE TONEXT PAGE
Yes
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Does the ABS warning light
remain illuminated
even
with the ECU connector dis-
connected?
YesNoShort in ECU transistor
1 Replace ECU.I

SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-25
MAINIGNITION
REVERSE SIDE DATA LINK
CONNECTOR
ICONTINUED FROM
PREVIOUS PAGE
III
I-
Can other electronic control _ No . Scan. tool related mal-systems communicate with
scan tool?Fhnc;;n. Repair
and re-
Yes
No c Correct cause of blown
fuse and replace fuse.
With the ignition key in the
_No) Is power relay normal?
“ON” position, does

,thf(Refer to P.35-74.)
;;I;; relay make a click
Disconnect ECU connector
and check harness connec-
tor.
I
14A0667
Yes
W
ith the ignition key in the
“ON” position, does voltage
between ECU connector ter-
minal No. 18 and ground in-
dicate the battery voltage?
Yes
Is there continuity between
body harness terminals
No. 9, No. 20 and No. 34, and
ground?
ECUground line broken
Yes
tpNo
Is there continuity betwee
n
Harness wire between
body harness connector
ter-data link connector and
minals
No.23 and No.24, andABS ECU is broken.
f2;;k connectors No.4 &
I
Repair harness.
Yes
Malfunction of ABS ECU Replace ABS ECU.
1
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35-26SERVICE BRAKES - Anti-lock Braking System Troubleshooting
CABS warning light does not illuminate when ignition key is in “START”\
position.
[Explanation]
The ABS ECU uses the IG2
power source which is
turned off in the “START” position. The
ABS
warning light uses the IGl power source which is
not turned off even in the “START” position
.
Consequently, in the “START” position, power is off and the ECU turns the valve relay OFF. If the
warning light does not illuminate at this time, there is trouble in the warning light circuit on the valve
relay side.
MAIN IGNITION
FUSIBLE
LINK @
1440677 Remove and inspect
10 pin connectors of
the hydraulic unit.
W
ith the ignition key in the
No
“ON” position, does voltage
c Harness wire between
HU and warning light is
between body connector broken.
terminal
No.8 and ground
indicate the battery voltage?
Yes
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Is there continuity between ,No
body connector termina
l
. Broken line between HU
No.9 and ground?
and body ground
Remove the valve relay. Is
Nothere continuity between Valve relay malfunction
terminal No. 87a and No. 30?
Replace valve relay. I
HU harness malfunction
IReplace HU.I

SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-27
DABS warning light blinks once after the ignition key is turned to the “\
ON” yFsiti?r!. It
illuminates in the “START” position and blinks once again when tur\
ned to the “ONpostilon.
[Explanation]
When power flows, the ABS ECU turns on th
e
harness between the ECU and the warning light, the
warning light for approximately 1 sec. while it light illuminates only when the valve relay is off in
performs a valve relay test. If there is a break in thethe valve relay test, etc.
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-.14AO681
Remove hydraulic unit
connector and ABS-ECU
connector and inspect at
L---J
the ABS-ECU harness
side connector.
In the ignition key “ON” _ No c Harness wire between
position, does voltage
be-ABS warning light and
tween terminal No.25
and ECU is broken.
ground indicate battery
vol-tage? I III
Yes
Malfunction of ABS ECU Replace ABS ECU.

35-28SERVICE BRAKES - Anti-lock Braking System Troubleshooting
E-l
I I
When the following diagnostic trouble codes are displayed “11 FL SPD \
SENSOR” “12
FR SPD SENSOR” “13 RL SPD SENSOR” “14 RR SPD SENSOR”I
[Explanation]
The ABS ECU detects breaks in the wheel speed
sensor wire. This diagnostic trouble code is output
if the wheel speed sensor signal is not input (or
short circuited) or if its output is low when starting
[Hint]
In addition to a broken wire/short circuit in the wheel
speed sensor, also check whether the sensor gap is
too large, rotor teeth are missing, sensor harness
wire is temporarily broken, or sensor harness and
to drive or while driving.
body connector are not properly inserted.
E-2 1 When diagnostic trouble code “15 SENSOR FAULT” is displayed
[Explanation]
This diagnostic trouble code is output when there isl Temporarily broken wire in sensor harness
an abnormality (other than broken wire or short cir-
cuit) in the wheel speed sensor output signal while
l Sensor harness and body connector are not
properly inserted.
driving.NOTE
[Hint](1) If contact is poor, check the sensor cable by
The following can be considered as the cause of thebending and lightly stretching it.
wheel speed sensor output abnormality.
(2) If there is currently no trouble and if abnormality
l Distortion of rotor, teeth missing in the displayed sensor circuit cannot be dis-,
lLow frequency noise interference when sensorcovered since values are normal even when
harness wire is broken checked, turn the ignition switch OFF and
l Noise interference in sensor signal re-execute the driving test. Try replacing the
l When the sensor output signal is below the ABS ECU only if the same diagnostic trouble
standard value or when amplitude modulation is
code is output at this time.
over the standard value,.using an oscilloscope to(If it is difficult to recreate the trouble, there is a
measure the wave shape of the wheel speed
possibility of speed sensor trouble recurring even if
sensor output signal is very effective.the ECU is replaced.)
l Loose wheel bearing
SPEED SENSOR
/~7FRONTREAR(LEFT SIDE) (RIGHT SIDE)(LEFT SIDE) (RIGHT SIDE)ggj ggjjm m
GND y23

y24
FRONT SIDE
REVERSDATA LINKCONNECTOR
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1440689

SERVICE BRAKES - Anti-lock Braking System Troubleshooting
Check flow connected with wheel speed
sensor
NOTE:When checking with an oscilloscope. first measure voltage variations in the wheel speed sensor output. (Refer to
P.35-69.)
Is the resistance value of the wheel speedNosensor part, which the displayed diagnos- -Malfunction of wheel speed) Replace wheel speed
sensor sensor.
tic trouble code indicates, normal?
Standard value:
0.8-I .2 kQ
Yes
Is the
resrstance v
connector normal? speed sensorRepair harness.
Standard value:
0.8- 1.2 kR
I
broken.
I Yes
Is the standard value for the
gap between the whee
l
speed sensor and rotor,
which the output diagnostic
trouble codeindicates,
within the range?
standard value:;y-0.9 mm (.012--035.
Yes
Yes
Check the output of each
wheel speed sensor with an
oscilloscope, including the
wave form. (Refer to mea-
surement of wheel speed
sensor output voltage varia-
tions on
P.35-69.) Is the out-
put voltage for each wheel
speed sensor over the stand- ard value and is the wave
form normal?
Yes
NoRecheck if below th
e
standard value or if the
sensor has a poor wave
form. Replace sensor or
rotor.
Can the abnormality be
Nofound even if the sensor harness and connection be-
tween sensor harness and body harness are bent and
stretched?
All the above checks are
_normal. There is a malfunc-tion of ABS ECU when this diagnostic trouble cod
e
reoccurs often.
I Replace the ABS
ECU
and check that the diag- nostic
trouble code does
not reoccur.
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