1991 MITSUBISHI ECLIPSE Service Manual

I
YesHU malfunctionReplace HU.
I

5-30BRAKES - Anti-lock Braking System Troubleshooting
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.
MAINIGNITIONFUSIBLELINK
@SWITCH(IGl)
ABS ECU
JCheck, using check chart
E-l -E-7.with the ECU connector
dis-
YesDoes the ABS warning light
NoShort in HU harness or
remainilluminated even
with the ECU connector dis-m sticking of valve relay
contact
connected?I
YesReplace HU or replace
valve relay.
ItShort in harness between
IT$Uhx ECU and ABS warningc Repair harness or replace
combination meter.

BRAKES - Anti-lock Braking System Troubleshooting5-31
SUBIGNITION
%TB(kEzYCH
IODE
;LLF-FIAGNOSIS
CONNECTOR
I Yes1,
With the ignition key in the
No _ Is power relay normal?
“ON” position, does the
(Refer to P.5-52.)power relay make a “click”:
noise?LDisconnect ECU connector
and check harness connec-Replace power relay.
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?
Yes
Yes
Replace ABS ECU.

5-32BRAKES -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 isand the ECU turns the valve relay OFF. If the
turned off in the “START” position. The ABSwarning light does not illuminate at this time, there
warning light uses the
IGI power source which isis trouble in the warning light circuit on the valve
not turned off even in the “START” position.relay side.
Consequently, in the “START” position, power is off
MAINIGNITIONFUSIBLESWITCHLINK @I(IGl)J/B
“62
I .1411213141516l7l61911112113114115U6i,79
@COMBINATIONAL METER
“58ABS ECU
1410000
hydraulicunit (HU) connector and
>\/I
1With the ignition key in the
“ON” position, does voltage
between body connector
terminal No.8 and ground
indicate the battery voltage?
Is there continuity between
No~Broken line between HU
body connector terminaland body groundNo.9 and ground?
I
YesIs there continuity between
HU connector terminal No. 8and terminal
No.9?
YesRemove the valve relay. Is
there continuity between
terminal No. 87a and No. 30?
I
Yes1 Replace valve relay.
HU harness malfunction
I
1 Replace HU.

BRAKES - Anti-lock Braking System Troubleshooting5-33
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 the
the valve relay test, etc.
Y
x %l4
9
4
n. 58
ABS ECU
14A0597
EC
4connector and check with
he harness connector. /\/
IIn the ignition key “ON”
position, does voltage be-
tween terminal
No.25 andground indicate battery vol-
tage?
Replace ABS ECU.I

5-34BRAKES -Anti-lock Braking System Troubleshooting
E-lInput abnormality of wheel speed sensorI.
[Explanation][Hint]s”rThe ABS ECU detects breaks in the wheel speed
In addition to a broken wire/short circuit in the wheel--sensor wire. The warning light lights up if the wheel
speed sensor, also check whether the sensor gap isspeed sensor signal RL is not input (or shorttoo large, rotor teeth are missing, sensor- harness
circuited) or if its output is low when starting to drivewire is temporarily broken, or sensor harness and
or while driving.body connector are not properly inserted.
E-2Output abnormality of wheel speed sensor
[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.
[Hinti
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
FRONTREARP%(LEFT SIDE)
(RIGHT SIDE)(LEFT SIDE)(RIGHT SIDE),’
1
FRONT SIDE
SELF-DIAGNOSISCHECK CONNECTOR14AO608

BRAKES - Anti-lock Braking System Troubleshooting5-35Check flow connected with wheel speed
NOTE:
sensorWhen checking with an oscilloscope, first measure voltagefl-variations in the wheel speed sensor output. (Refer to P.5-51.)Is the resistance value of the wheel
speed sensor part, which the displayed
No cMalfunction of wheel speed _~ Replacewheel speedsensor
sensor.trouble code indicates, normal?
Standard value:
0.8-l .2 kQIs the resistance value with the ECU
No* Harness
wireforwheelRepair harness.connector normal?
speedI
broken.Is the standard value tor the
gap between the wheel
speed sensor and rotor,
which the output trouble
code indicates, within the
range?Standard value:
h;ti;j3-0.9 mm (.012-Rear
Nb adjustment
- No
the wheel speed sensor. Replace rotor that has
rotor that the trouble code
missingor damaged
indicates, normal and withteeth.
missing or damaged
Check the output of each
wheel speed sensor with an
oscilloscope, including the
wave form.
(Refewhekqmeasurement of
speed sensor output voltage
variations on
P.5-51.) Is the
output voltage for each
wheel speed sensor over
the standard value and is thewave form normal?I
YesCan the abnormality be
found even if the sensor
harness and connection be-
tween sensor harness and
body harness are bent and
stretched?
No
Repair harness.

5-36BRAKES - Anti-lock Braking System Troubleshooting
E-3Abnormality of G sensor circuit
[Explanation]The ABS ECU turns on the warning light in the
following cases.
lOFF trouble turning G sensor OFF (It is judged
that the
G sensor continues to be OFF for more
than approximately 13 seconds except when the
lWhen there is a broken wire or short circuit in
the harness for the
G sensor system.
PlUN; F;SIBLEIGNITIONSWITCH (IG2)J/B
G-SENSOR
E-lABSECU
14AO609
Is G sensor normal? (ReferNoto
P.5-86.)Replace G sensor.
I YesWith the ignition key “ON”
_ No m The harness between the
does the voltage betweenG sensor and the ABS
terminal No.6 and groundECU is broken.
indicate battery voltage?
IG sensor circuit is normal.I