key MITSUBISHI 3000GT 1991 Owner's Guide

35-16SERVICE BRAKES -Anti-lock Braking System Troubleshooting
BABS warning light stays on when the ignition key is in the “ON” position.
[Explanation]
[Hint]
This is the symptom when the ABS ECU does not
Check the diagnosis output and if there is no output
power up due to broken ECU power circuit, etc.,
voltage or if the MUT and ABS ECU cannot
when the fail safe function operates and isolates thecommunicate, there is a good possibility that power
system or when the warning light drive circuit is
is not flowing to the ECU.
short circuited.
!8IGNIISWIT(-
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C151
:
E
COMBINATION
METER
-19
7
------____-_---1
2
610 2
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6227J
r bL-1
IN(IGl)
1
,
ig
)
158
7
r-TSB iCaution
lIf the trouble code is output, the system can
be in the fail safe mode. in such a case, erase
the trouble code and then restart the engine
to check if the system is currently in a fault
condition.
~~~~
~~~~1
I,No ,I
Yes6
Replace ECU.
41,No rIDoes the ABS warning light
remain illuminated even with
the HU connector discon-
nected?
Yes
Short-circuit in harness
between HU or ECU and ABS
warning light
> Repair harness or replace
combination meter.
bvision

SERVICE BRAKES -Anti-lock Braking System Troubleshooting3547CONTINUED FROM
PREVIOUS PAGE
ABS
POSER
RELAY
DIODE
SELF-LM&OS'S
CONNECTOR
FRONT
SIDEYes
Is power relay normal?
(Refer to
P.35-62.)
-Replace power relay.
With the ignition key in the
“ON” position, does voltage
between ECU connector
terminal No. 18 and ground
indicate the battery voltage?
I
1YesNo
-
I--Harness wire between
power relay and ECU
is brokenJ1Repair harness.
I
~ No
Is there continuity betweenrbody harness connector ter-agnosis inspection ter-
minals No. 23 and No. 24,minal and ABS ECU is
and diagnosis inspection ter-
minals No. 4 & No. 1 O?Yes
”Malfunction of ABS ECUReplace ABS ECU.
TSB Revision

35-18SERVICE BRAKES -Anti-lock Braking System Troubleshooting
CABS warning light does not illuminate when the ignition key is in the “START” position.
[Explanation]
LJThe ABS ECU uses the
IG2 power source which is
turned off in the “START” position. The ABS
warning light uses the
IG, 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.
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::9
IG-R l,,l G-6
7
COMBINATION
METER
.- ------ ---_-__1
‘$2 1274
7
sE,
85
ON(IGl)
1
;ABS
ECU
H
(--)With the ignition key in the
indicate the battery voltage?
Yes
Yes
I
Yes*Replace valve relay.
HU harness malfunction
NOTEWhen performing the check marked *, note polarity of the diode
(refer to the circuit diagram).
vision

SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-19
DABS warning light blinks once after the ignition key is turned to the “ON” position. It
(L.-Jilluminates in the “START” position and blinks once again when turned to the “ON” position.
[Explanation]
When power flows, the ABS ECU turns on theharness between the ECU and the warning light, the
warning 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.
IGNITIONSWITCH(IG1)
I
COMBINATION
METER
58
g:"I 2
3
mi
456788 7
ASS-ECUIn the ignition key “ON”
position, does voltage
between terminal No. 25 andground indicate battery
voltage?ABS warning light andECUis broken.
Yes
Repair harness.
vMalfunction of ABS ECU
+ Replace ABS ECU.
TSB Revision

35-24SERVICE BRAKES -Anti-lock Braking System Troubleshooting
E-5When diagnosis code “51 VALVE RELAY” is displayed
[Explanation]
When the ignition switch is turned ON, the ABS
ECU switches the valve relay OFF and ON for an
initial check, compares the voltage of the signal to
the valve relay and valve power monitor line voltage
to check whether the valve relay operation isnormal. In addition, normally it monitors whether or
not there is power in the valve power monitor line
since the valve relay is normally ON. Then, if the
supply of power to the valve power monitor line is
interrupted, this trouble code will be output.
EPfiiB EenIGNITIONSWITCH(IG1)
COMSINATIONm
I
H” g@J$s2
4:u
,,8I. -----I/IL’ /
IIII
I /IIII/I/-,----__--_,>yo “-a-‘+G ------------------ ?$”:
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i.-I
1/2131a)5161718(QIIO(I ~~~2(13~~a~i5~~6/i7~~~IQ$O~Y~2~3~24~~6~~~28~~~1~2~3~4~5~Remove and check the valve relay.
IWhen the valve relay is checked, are
the following conditions found?
No. 85
-No. 86: Resistance
value 60 - 120 fiNo. 30-No. 87a: Continuity
No. 30 - No. 87: No continuity
When battery voltage is applied
between terminals No. 86 and No. 85.
No. 30
- No. 87: Continuity
No. 30 - No. 87a: No continuity
Yes
Install the valve relay and remove
the HU connector.
E+GG-pqReplace valve relay.
&I/ NnIIWith the ignition key “ON”, does the
Is there continuity between HU No. 8
and No. 7 terminals?
IYes
Connect the HU harness and remove
the ECU connector.Faulty harness in HU
1Does resistance between body con-
nector terminal No. 2 and terminal
No. 27 indicate 60
- 120 II
NoMalfunction of harness
between HU and ECU.
Yes
With the ignition key “ON”, does the
voltage between terminal No. 22 and
ground indicate battery voltage?
YesNo
II- Malfunction of harness
between HU and ABS
ECU.Repair harness.
vision

35-26SERVICE BRAKES -Anti-lock Braking System TroubleshootingI
TROUBLESHOOTING (ABS - AWD)Confirm condition in the following way and diagnosis accordingly.
Does the ABS warning light illuminate as described
below up to the time the engine starts?(2) With the ignition key in the “START” position,
(1) When the ignition key is turned to the “ON”power to the ABS ECU is interrupted and the
position, the ABS ECU causes the ABS warningABS warning light remains lit because the valve
relay is OFF.
light to flash four times in about one second (3) When the ignition key is returned from the
(during which the valve relay self check is made)
and then causes it to go out.“START” position to the “ON” position, the
ABS warning light flashes four times in about
one second (during which the valve relay self
-check is made again) and then goes out.
III
OFFu--I-II
ST
ONACC, LOCK
114A0594Yes
>CONTINUED ON NEXT PAGE
No
No.
Trouble condition
Major causesRemedy
1ABS warning light does not light up at all.l ABS warning light bulb is burnt out.
ACC,LOb--
l Open in ABS warning light electricalCheck, using flowchart A (Refer to
ABScircuit (check for blown fuse)P.35-31.)warningOFFlight
lgmtlon
key
14AO590
2When the ignition key is turned to the
“ON” position, it remains lighted.l Fail safe is functioning due to ECU
self diagnosis.Check, using flowchart B (Refer toABS,“,F
J-l Short in ECU warning light drive circuitP.35-34.)warningl Malfunction of ECUlight
Ignition
key.;i,LOi h
3Does not illuminate when ignition key is
in “START” position.l Malfunction of valve relayl Break in harness between ABS warningCheck, using flowchart C (Refer to
light and HUP.35-36.)l Break in harness between HU andwarning
body ground
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SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-27
i-,’
No.
4Trouble condition
IMajor causes
After the ignition key is turned to the
“ON” position, it blinks once and then
illuminates when it is turned to the
“START” position. When the key is
returned 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.)
ABSwarrmglightkey ACC.
LOi;+lgmtion14A0593l Break in harness for ECU warning
light drive circuit
l Malfunction of ECU
CONTINUED FROM PREVIOUS PAGE
Yes
Trouble condition
One-sided braking
Insufficient braking force
Decline in ABS function
ABS sometimes functions even when
there is no sudden braking.
(ABSoperation vibration is transmitted.)Remedy
Check, using flow
chart D (Refer to
P.35-37.)Does the ABS warning light illuminate
when starting to drive the car?Trouble with the motor relay, solenoid
valve [due to self test at start-up or
Is there one-sided braking, insufficient
braking force or malfunction of ABSCONTINUED ON NEXT PAGE
Major causes
l Hydraulic line in HU is clogged.
l Mechanical lock of HU solenoid valve
l Hydraulic line in HU is clogged.
l Malfunction in HU solenoid valve
operation
l Insufficient wheel speed sensor out-
put voltage (sensor malfunction, too
large a gap between sensor rotor,
missing rotor teeth)
l Malfunction of ABS ECURemedy
Check HU operation and, if
necessary, replace
HU.If HU is normal, check struc-
tural parts for normal
braking.
Check wheel speed sensor
(Refer to
P.35-57.) and, if
necessary, replace sensor,
adjust gap or replace rotor.
If tests indicate that there are
no mechanical or electrical
failures,replace the ECU.
TSB Revision

35-32SERVICE BRAKES -AniLlock Braking System Troubleshooting
NoWith the ignition key in the “ON” posi-
I--Check fuse No. 11. If it is
blown, correct the cause of
the blown fuse and then
replace the fuse.J
Yes
I
( ~;T&$Efg,?~ )harness connector terminal
No. 59 and ground indicate
battery voltage?
----F--
&Repair harness.
Circuit in combination meter
-is broken.
Is there continuity between combination
meter No. 58 and No. 59 terminals?
Are instrument panel wiring harness
and body wiring harness connected
Broken wire in ECU, valve relay or both
drive circuits. Check both circuits.
TSB Revision

SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-33
1i, 1 CheckABSECU. ,
Remove the ECU connector and
check.Does the voltage between ECU harness
> Broken wire between ABSj Repair harness.
connector terminal No. 25 and ground
warning light and ECU
indicate battery voltage while the
ignition key is in the “ON” position?
Yes
> ABS ECU malfunction> Replace ABS ECU.
Remove valve relay and check.
I
1Nois valve relay normal? (Refer to
P.35-62.)) Valve relay malfunction+ Replace valve relay.IYes
Install the valve relay, remove the HU
connector and check.
Does voltage between the HU harness
uLEm-h[ Repair harness.
connector terminal No. 8 and ground
indicate battery voltage
while the
ignition key is in the “ON” position?
Yes
r7; t%$~?$!Je~~~g~undIIs there continuity between HU harness9 Repair harness.
connector terminal No. 9 and ground?
Is there continuity between HU harness
connector terminals No. 8 and No. 9?Yes+ HU malfunctionI+ Replace HU.
b Connector not connected
securely.- Replace connector.
1 TSB Revision

35-34SERVICE BRAKES -Anti-lock Braking System Troubleshooting
II1
1 B 1 ABS warning light stays on when the ignition key is in the “ON” position.1II\[Explanation]
[Hint]
k.JThis is the symptom when the ABS ECU does not
power up due to broken ECU power circuit, etc.,Check the diagnosis output and if there is no output
when the fail safe function operates and isolates thevoltage or if the MUT and ABS ECU cannot
system or when the warning light drive circuit iscommunicate, there is a good possibility that power
short circuited.is not flowing to the ECU.
IGNITIONSWITCH(IG1)Caution
lIf the trouble code is output, the system can
be in the fail safe mode. In such a case, erase
the trouble code and then restart the engine
to check if the system is currently in a fault
condition.
f
j @
?
j 0
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Y
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I25ABS
ECU
iz- 11213 ia1516j7j819~10~11~12~13~14~15~16~17~1819l20l21C2C3Ca~25~~7~3~29~0~1~32~3~35
:95-AK-R9502
4
Replace ECU.
I YesI.
Replace HU or replace
valve relay.
I
_
ai.. .
ITSB hevIsIon