1991 MITSUBISHI ECLIPSE ECU

5-24BRAKES - Anti-lock Braking System Troubleshooting
E-6 Abnormality of motor drive circuit
[Explanation]The ABS ECU illuminates the warning light for the
motor relay and motor in the following cases.
l When the motor relay does not function
lWhen there is trouble with the motor itself and it
does not revolve
lWhen the motor ground line is disconnected and
[Hint]If there is motor operation noise when wheel speed
exceeds
Gkm/h (4mph) when starting up after the
engine is started, there is a broken or short circuitedmotor monitor wire.
the motor does not revolve
l When the motor continues to revolve
14A0605Does the motor make a
YesBroken wire or short cir-noise when wheel speedcuit in motor monitor line
exceeds 6 km/h (4 mph)?
1Repair the harness be-
tween HU and ECU.
, NoRemove the motor relay.
Remove the motor relay andcheck resistance values.
No. 85-No. 86:resistancevalue
30-60 52No.30-No.87: no continui-
ty
Battery voltage is applied onterminals No. 86 and No.85
grounded.No.30-No.87: continuity
IYesIs pump motor ground con-
NoConnect ground wire.
netted normally?
IlYes
motor relay and re-
move HU connector.>Does voltage between body
connector terminal 51 and
No c Broken wire in pump
motor power circuit
ground indicate battery vol-
tage?4Repair the harness.
YesIs resistance between body
NoMalfunction of harnessconnector terminal No. 2 andbetween HU and ECUNo.26 30-60 ohms?iII1Repair harness.

BRAKES - Anti-lock Braking System Troubleshooting5-25
TROUBLESHOOTING (ABS-AWD)Confirm condition in the following way and diagnosis accordingly.
C
F
>oes the ABS warning light illuminate as described
relow 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 four times and goes out and stays
out.power to the ABS ECU is interrupted and the
ABS warning light remains lit because the valve
relay is OFF.
t:2) With the ignition key in the “START” position,(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 four times
and then goes out and stays out.IO1
-1 sec. 1 sec.1
sec.1 sec.
14AO594
YesCONTINUE TO NEXT PAGE
No
No.
1
2
3
Trouble condition
ABS warning light does not light up at all.
ABSwarninglightOFFIgnitionkey
ACC.
LO;-+
14AOSSOWhen the ignition key is turned to the
“ON” position, it remains lighted.
4BSNamingight
0:7gnition
wACC.
LO:+14A0591Does not illuminate when ignition key is
in “START” position.
4BSNamingightONOFF
14A0595
Major causes
l ABS warning light bulb is burnt out.
l Open in ABS warning light electrical
circuit (check for blown fuse)
l Fail safe is functioning due to ECU self
diagnosis
l Short in ECU warning light drive circuitl Malfunction of ECU
l Malfunction of valve relay
l Break in harness between ABS warn-
ing light and HU
l Break in harness between HU and
body groundRemedy
Check, using flow
chart A. (Refer to
P.5-27.)
Check, using flow
chart B. (Refer to P.5-30.)
Check, using flow
chart C. (Refer to
P.5-
32.)

5-26BRAKES - Anti-lock Braking System Troubleshooting
No.Trouble conditionMajor causesRemedyAfter the ignition key is turned to the
l Break in harness for ECU warningCheck, using flow“ON” position, it blinks once and thenlight drive circuitchart D. (Refer to P.5-illuminates when it is turned to the
l Malfunction of ECU33.)“START” position. When the key is
returned to the “ON” position, the light
4blinks again. (Blinking with the ignition
key in the “ON” position is synchronized
with operation noise of the valve relay.)
ABSwarning
light
0:~
Ignition
keyACC. iv-
14A0593CONTINUED FROM
PREVIOU? PAGE
I ,
Does the ABS warning light illuminateYes* Check, following trouble
when starting to drive the car?L Trouble with the motor re-lay, solenoid valve [due to
self test when driving above
6 km/h (4 mph)] or malfunc-source check charts E-l -E-7.
Notion of wheel speed sensor
Normal
YesTrouble condition
Major causes
RemedyOne-sided brakingl Mechanical lock of HU solenoid valveCheck HU operation and, if
Insufficient braking forcel Hydraulic line in HU is clogged.
necessary, replace HU.
If HU is normal, check
Decline in ABS functionl Malfunction in HU solenoid valve op- structural parts for normal
(Wheels easily lock when there is
sud-
erationbraking. (Refer to P.5-2.)den braking.)l Hydraulic line in HU is clogged.
ABS sometimes functions even whenl Insufficient wheel speed sensor
out-Check wheel speed sensor
there is no sudden braking. (ABS opera-put voltage (sensor malfunction, too (Refer to P.5-82.) and, if
tion vibration is transmitted.)
large a gap between sensor rotor, necessary, replace sensor,
missing rotor teeth or temporarily adjust gap or replace rotor.
broken wire in sensor harness)
If tests indicate that there are
l Malfunction of ABS ECU
no mechanical or electrical
failures, replace the ECU.

BRAKES - Anti-lock Braking System Troubleshooting5-27
AABS warning light does not light at all.I-. [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.
MAIN FUSIBLE
LINK
@
2
c-4
I 1~0~0~fWW-i
m2 ac
HU&,52&8--1
III
IA x A ,c
VALVE "I
RELAYI
1 IRELAY /--+I1 &-I I
\, J,. \ ,I L-1
I-----------A
I I
[Hint]If other warning lights do not light up either, fuse is
probably blown.
IGNITIONIGNITIONSWITCH (IG2)SWITCH (IGI)
10A10A p,
*2\I6-IM"
7,,14112131415161718I 9 I
iE4~oWERI.0(1111211311915116117
#$II;NATION
58
ABS ECU125
GNDGNDT7”

5-28BRAKES -Anti-lock Braking System Troubleshooting
With the ignition key in the “ON”
posi-NoCheck fuse No.ll. If it is
tion, do other warning lights illuminate?blown, correct the cause of
the blown fuse and then
replace the fuse.
YesTurn the ignition switch OFF and
Does voltage between
har-NOThe harness between the
nessNo. 14 and ground indicate
battery voltage?) fuse No.1 1 is broken.
YesCircuit in combination meter
is broken.
tRepair or replace com-
bination meter.II
IIIs the ABS warning light normal? (CheckNO) ABS warning light bulbReplace ABS warning
for burned bulb.)
burned.* light bulb.
I
Yes
- No
Are instrument panel wiring harness,
engine compartment wiring harness,
body wiring harness and ABS wiring
harness connectors connected properly?
c Connect connectors firmly.
(Check for pins pulled out or
bent, repair as needed.)
YesBroken wire in ECU, valve relay or both
drive circuits. Check and repair both
circuits.

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.