1989 MITSUBISHI GALANT Service Repair Manual

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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35-30SERVICE BRAKES - Anti-lock Braking System Troubleshooting
E-3When diagnostic trouble code “22 STOP SW” is displayed1
[Explanation][Hint]
The ABS ECU outputs this diagnostic trouble codeIf the stop light operates normal, the ABS harness
in the following cases.wire for the stop light switch input circuit to the ECU
lStop light switch may remain on for more thanis broken or there is a malfunction in the ABS ECU.
15 minutes without the ABS functions.
lThe harness wire for the stop light switch may be open.
SUB FUSIBLELINK @
ABSECU
[1121314/5161716~9~10~11~12~13~14~15(16~17~18]~19DOC1122~3~4125l26~27~2~2913013ll3Z~33(341351
Do the stop lights light up
and go out normally?No c Check the stop light re-
lated circuit and repair
problem spots.
Yes
connector and inspectat
the harness side connec-
When the brake pedal is
_NoHarness wire between
pressed forcefully, does the
voltage between connector stop light switch and ABS
ECU is broken.
terminal No. 29 and ground
indicate battery voltage?
c
Repair harness.
Yes r
Malfunction of ABS ECU Replace ABS ECU.
I
14AO683
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SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-31
E-4When diagnostic trouble codes “41 SOL
V
FRONT L”, “42 SOL V FRONT R” OR “43
SOL V
REAR” are displayed
[Explanation]
The ABS ECU normally monitors the solenoid valve
drive circuit.
If no current flows in the solenoid even if the ECU
turns the solenoid ON or if it continues to flow even when turned OFF, the ECU determines the solenoid
coil wire is broken/short circuited or the harness is
broken short circuited and then these diagnostic
trouble codes are output.
IGNITION
SWITCH
(IGl)
U
0
&
cY10
2: p:\
,8 , ---------7HUI1 I
Ll 12 [ 3 14 [ 5 16 1 7 18 ~9110/11112113114115116117l18I~19~0~1~22~3~24~25~26~27~28)29~30~31~32~33~~~35~
tor and check with the HU
\/
Is the resistance value for the
solenoid valve, that the dis-
played diagnostic troublecode indicates, within the
range of the standard values?
Standard value:
1.07-1.17 52
Is the solenoid valve resist-
ance value, that the output
diagnostic trouble code dis- plays, within the range of the
standard values when mea-sured at the ECU connector?
Standard value:
1.07-1.17 Q
Replace HU.
NoThe harness wire for the
solenoid valve
circuit
whose resistance value is outside the range of thestandard value is broken
or short circuited.
I
Repair ABS harness.
Malfunction of ABS ECU Replace ABS ECU.
I
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