1991 MITSUBISHI ECLIPSE Service Manual

BRAKES - Anti-lock Braking System Troubleshooting5-13With the ignition key in the “ON”
posi-Nol
tion, do other warning lights illuminate?
II
YesCheck fuse No. 11. If it is
blown, correct the cause of
the blown fuse and then
replace the fuse.
Does voltage between
har-NoThe harness between thenessconnector terminalcombination meter from
No. 14 and ground indicate) fuse No.1 1 is broken.
battery voltage?
II
Yes
Repair harness.Circuit in combination meter
is broken.Repair or replace
com-
* bination meter.
Turn the ignition switch OFF an
(check.
IIs the ABS warning light normal? (Check
for burned bulb.)
No L A&zed%rning light bulb -Are instrument panel wiring harness,
_Noengine compartment wiring harness,~ Connect connectors firmly.
(Check for pins pulled out or
bent, repair as needed.) body wiring harness and ABS wiring
harness connectors connected properly?drive circuits. Check and repair both

5-14BRAKES - Anti-lock Braking System Troubleshooting
aCheck ABS ECU.
Does the voltage between ECU harness
Not Broken wire between ABSRepair harness.connector terminal No.25 and groundwarning light and ECU
indicate battery voltage?
Yes
Replace ABS ECU.Check ABS valve relay.
I

Is valve relay normReplace valve relay.I
YesInstall the valve relay and, with the
(gnition key in the “ON” position>remove the HU connector and check.
IDoes voltage between the HU harnessNow Broken harness wire be-connetor terminal No.8 and ground
indi-tween ABS warning light
cate battery voltage?and HU
Yes
7II1/---I Repair harness.
Is there continuity between HU harnessNo* Broken harness wire be-Repair harness.connector terminal No.9 and ground?tween HU and groundI
YesHU malfunction
Replace HU.

BRAKES - Anti-lock Braking System Troubleshooting5-15
--
BABS warning light illuminated after the engine is started and remains on.
[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 thesystem or when the warning light drive circuit is
short circuited.
MAINIGNITION
FUSIBLELINK
@IEYCH
z
A:7
J/B
rb
0
10A
I
:c
r
I
1vAI23
f
! 127ABS ECUCheck, using check chart
E-l -E-6.Check warning light drive
circuit.
t
Does the ABS warning lightNoShort in ECU transistor
remainilluminated even
with the ECU connector dis-
connected?
I
1 YesIReplace
I
Does the ABS warning light
remainilluminated even
with the ECU connector dis-
connected?
Yes
IReplace HU or replacevalve relay.I

5-16BRAKES - Anti-lock Braking System Troubleshooting
SUB
IGNITION
FUSIBLE
SWITCHLINK
@W.2)
I I18
ABS ECU9
SELF-DIAGNOSISCHECKCONNECTOR
No - Correct cause of blown
fuse and replace fuse.
YesWith the ignition key in the
“ON” position,
does ,thf
E;;;; relay make a click
’ Yes ’Disconnect ECU connector
and check harness
connec-
tor.
YesWith the ignition key in the
“ON” position, does voltage
between ECU connector ter-
minal No. 18 and ground in-
dicate the battery voltage?
---j-z-
III
I -11 Repair harness.I
YesMalfunction of ABS ECU
Replace ABS ECU.

BRAKES - Anti-lock Braking System Troubleshooting5-17
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
IGI power source which is
not turned off even in the “START” position.
Consequently, in the “START” position, power is offand 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.
MAINIGNITIONFUSIBLESWITCHLINK @(iG1)I
J/B58
15
ABS ECUWith the ignition key in the
“ON” position, does voltagebetween body connector
terminal
No.8 and groundindicate the battery voltage?
Yes

5-18BRAKES - Anti-lock Braking System Troubleshooting
DABS warning light blinks once after the ignition key is turned to the “ON” position. It
illuminates in the “START” position and blinks once again when turned to the “ON” position.
[Explanation]
When power flows, the ABS ECU turns on the
harness between the ECU and the warning light, thewarning light for approximately 1 sec. while itlight 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.
125
El
ABS ECU
14A0597connector and check with
I
In the ignition key “ON”
_ No ~ Harness wire between
position, does voltage
be-ABS warning light and
tween terminal No.25 andECU is broken.
ground indicate battery vol-
tage?
YesRepair harness.
tMalfunction of ABS ECU
Replace ABS ECU.

BRAKES - Anti-lock Braking System Troubleshooting549
E-lInput abnormality of wheel speed sensorI-[Explanation][Hint]The ABS ECU detects breaks in the wheel speed
In addition to a broken wire/short circuit in the wheelsensor wire. The warning light lights up if the wheel
speed sensor, also check whether the sensor gap isspeed sensor signal is not input (or short circuited)
too large, rotor teeth are missing, sensor harness
or if its output is low when starting to drive or while
wire is temporarily broken, or sensor harness and
driving.body connector are not properly inserted.
I IE-2Output abnormality of wheel speed sensorI
[Explanation]The warning light lights up when there is an
abnormality (other than broken wire or short circuit)
in the wheel speed sensor output signal while
driving.
[Hint]
The following can be considered as the cause of thewheel speed sensor output abnormality.
l Distortion of rotor, teeth missing
lLow frequency noise interference when sensor
harness wire is broken
l Noise interference in sensor signall When the sensor output signal is below the
standard value or when amplitude modulation is
over the standard value, using an oscilloscope tomeasure the wave shape of the wheel speed
sensor output signal is very effective.
l Loose wheel bearing
l Temporarily broken wire in sensor harness
l Sensor harness and body connector are not
properly inserted.
NOTE
If contact is poor, check the sensor cable by bendingand lightly stretching it.
SPEED SENSOR
FRONTREAR(LEFT SIDE) (RIGHT SIDE) (LEFT SIDE) (RIGHT SIDE)
Km
I-.IIGND
III24I
FRONT SIDE
I
ABSECU
REVERSE SIDE
SELF-DIAGNOSIS
CHECK CONNECTOR
14AO601

5-20 _BRAKES - Anti-lock Braking System TroubleshootingCheck flow connected with wheel speed
sensorNOTE:When checking with an oscilloscope, first measure voltage
variations in the wheel speed sensor output. (Refer to
P.5-51.)
Is the resistance value of the wheelNo c Malfunction of wheel speedReplace wheel speed
speed sensor part, which the displayedsensor
sensor.trouble code indicates, normal?
Standard value:
0.8-l .2 kQ
I YesIs the resistance value with the ECU
No c Harness wire for wheel -Repair harness.connector normal?
speed
sensorcircuit is
Ibroken.
II1
1
Is the standard value for the
gap between the wheel
speed sensor and rotor,
which the output trouble
code indicates, within the
range?
Standard value:
h
%Z~Pf!;!~~~e~no missing or damaged
teeth?
1 Yes
1Check the output of each
wheel speed sensor with an
oscilloscope, including the
waveform. (Refer to
measurement ofwheel
speed sensor output voltage
variations on
P.5-51 .I Is the
output voltage for each
wheel speed sensor over
the standard value and is thewave form normal?
Yes
Canthe abnormality beNoRepair harness.foundeven if the sensorIharness and connection be-
tween sensor harness and
body harness are bent and
estretched?
Yes