warning light MITSUBISHI ECLIPSE 1991 Service Manual

BRAKES - Anti-lock Braking System Troubleshooting5-9
ANTI-LOCK BRAKING SYSTEM
-- TROUBLESHOOTINGNO!JEBAE
PARTICULAR CHARACTERISTICS OF
THE ANTI-LOCK BRAKING SYSTEMModels equipped with the anti-lock braking system
(A.B.S.) may exhibit one or more of the following
characteristics from time to time, but none of these
is abnormal.
(1) A pulsing feeling in the brake pedal, or vibration
of the body or the steering wheel, when the
anti-lock braking system is activated by sudden
braking or by braking on a slippery road surface.Actually, this phenomenon is an indication that
the anti-lock braking system is functioning nor-
mally.(2) When the vehicle speed reaches approximately
6 km/h (4 mph) after the engine is started and
the vehicle starts off (for the first time), a
whining motor noise may be heard from the
engine compartment if the vehicle is traveling in
a quiet place, but this noise is simply the result
of a self-check being made of the anti-lock
braking system operation.
TROUBLESHOOTING METHODSProblems related to the anti-lock braking system
(A.B.S.) can be classified into two general categor-
ies: problems in the electrical system and those in
the hydraulic system.For problems in the electrical system, the
self-diagnosis function is built into the electronic control
unit (E.C.U.) causing the A.B.S. warning light to
illuminate as a warning to the driver.
Problems in the hydraulic system (poor braking,
etc.) can be located in the same way as for ordinary
brakes. There is, however, the necessity to check todetermine whether the problem is related to ordin-
ary brake components or to the components relatedto the A.B.S.
HOW TO USE THE TROUBLESHOOTING
FLOW CHART(1) Using the flow chart, check the ABS warning
light light-up sequence and check the condition
of braking operation.
(2) Following the check chart listed in the remedy
column, perform the checks. There are [Explana-tion] and [Hint] in each check chart. Refer to
them when troubleshooting.
NOTEECU: Electronic control unit
HU: Hydraulic unit
MUT: Multi-use tester

Ioes the ABS warning light illuminate as describedbelow up to the time the engine starts?
1) When the ignition key is turned to the “ON”
position, the ABS warning light illuminates for
approximately 1 second due to the ABS ECU (asa self check of the valve relays is performed),
then it blinks twice and goes out and stays out.
2) With the ignition key in the “START” position,
power to the ABS ECU is interrupted and the
5-10BRAKES - Anti-lock Braking System Troubleshooting
TROUBLESHOOTING (ABS-FWD)Confirm condition in the following way and diagnosis accordingly.
ABS warning light remains lit because the valve
relay is OFF.
(3) When the ignition key is turned from the
“START” position to the “ON” position, the
ABS warning light illuminates for approximately
1 second (during this time a recheck of the valverelays is performed), then it blinks twice and
then goes out and stays out.
ABS warning
lightON
OFF
1Ignition
kev
ST
ON
ACC, LOCK
IYes
CONTINUE TO NEXT PAGE
No
No.Trouble condition
ABS warning light does not light up at all.
ON
1 --ABSwarningOFF
1lightlgnitlon
kev
14A0590When the ignition key is turned to the
“ON” position, it remains lighted.
ABSwarning
2light
Ignition
kevACC,
LO:+14AOSQlDoes not illuminate when ignition key is
in “START” position.
ABSONwarning
3lightOFFUULkev ACC.
LO:-+-Ignition14A0592
1 sec. 1 sec.1 sec.1 sec.
---
IIII
3114AO589
IMajor causes
l ABS warning light bulb is burnt out.Check, using flow
l Open in ABS warning light electricalchart A (Refer to P.5-
circuit (check for blown fuse)12.)
l Fail safe is functioning due to ECU selfdiagnosis
o Short in ECU warning light drive circuitl Malfunction of ECU
l Malfunction of valve relayl Break in harness between ABS warn-
ing light and HU
l Break in harness between HU and
body groundRemedy
Check, using flow
chart
B (Refer to P.5-
15.)
Check, using flow
chart C (Refer to P.5-17.)

BRAKES - Anti-lock Braking System Troubleshooting5-14
./
No.Trouble conditionMajor causesRemedyAfter the ignition key is turned to the
l Break in harness for ECU warningCheck, usinflow
“ON” position, it blinks once and then
light drive circuit
chart D. (Re er to9illuminates when it is turned to the
l Malfunction of ECUP.5-18.)“START” position. When the key is
4returned to the “ON” position, the light
blinks again. (Blinking with the ignition
key in the “ON” position is synchronized
with operation noise of the valve relay.)
ABSwarninglighto:-
Ignition
keyACC. LCi+-
14*0593CONTINUED FROM PREVIOUS PAGE
Does the ABS warning light illuminate
when starting to drive the car?
Yes~ Trouble with the motor re-lay, solenoid valve [due toL Check, following trouble
source check charts E-l -self test when driving above
E-6.6 km/h (4 mph)] or malfunc-
NoIs there one-sided braking, insufficient
braking force or malfunction of ABS
operation?
YesTrouble condition
Major causes
One-sided braking
Insufficient braking forcel Mechanical lock of HU solenoid valve
l Hydraulic line in HU is clogged.
Decline in ABS function
(Wheels easily lock when there is sud-
den braking.)
ABS sometimes functions even when
there is no sudden braking. (ABS opera-
tion vibration is transmitted.)
1 tion of wheel speed sensor 1
NoNormall Malfunction in HU solenoid valve op-
erationl Hydraulic line in HU is clogged.
l Insufficient wheel speed sensor out-
put voltage (sensor malfunction, too
large a gap between sensor rotor,
missing rotor teeth or temporarily
broken wire in sensor harness)
l Malfunction of ABS ECU
RemedyCheck HU operation and, if
necessary, replace HU.
If HU is normal, check
structural parts for normal
braking. (Refer to
P.5-7.)Check wheel speed sensor
(Refer to
P.5-82.) and, ifnecessary,replace sensor,
adjust gap or replace rotor.
If tests indicate that there are
no mechanical or electrical
failures, replace the ECU.

possibility that there is trouble with ABS warning
light or with power to the light.probably blown.
MAIN FUSIBLE
LINK @
5-12BRAKES - Anti-lock Braking System TroubleshootingA ABS warning light does not light at all.
I_
[Explanation][Hint]When it does not
liuht ULI at all, there is a strongIf other warning lights do not light up either, fuse is
IGNITIONSWITCH (IG2)IGNITIONSWITCH (IGl)
10A +,
“2.I6
-1z
v,,14TO ABS
I
” IPOWERIs&h ICOMBINAT~~N
ABS ECU
IGND GNDGNDv v vI
-14AO596

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

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