MITSUBISHI 3000GT 1991 Service Manual

SERVICE BRAKES -Anti-lock Braking System Troubleshooting
L’
No.Trouble condition\4
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.)
ABSwarninglight
key ACC. L::+
Ignition
14A05931 CONTINUED FROM PREVIOUS PAGE
1Major causes
l Break in harness for ECU warning
light drive circuit
l Malfunction of ECU
Does the ABS warning light illuminate
when starting to drive the car?
iIs there one-sided braking, insufficient
>CONTINUED ON NEXT PAGEI
I
YesTrouble condition
One-sided braking
Insufficient braking force
ABS sometimes functions even when
there is no sudden braking.
(ABSoperation vibration is transmitted.)Remedy
Check, using flow
P.35-19.)Remedy
l Check HU operation and, if
l necessary, replace HU.
If HU is normal, check struc-
l
HydraJicl Malfunction in HU solenoid valvetural parts for normal
braking.
Insufficient wheel speed sensor put voltage (sensor malfunction, too
large a gap between sensor rotor,
l Malfunction of ABS ECU(Refer to
P.35-57.) and, if
necessary, replace sensor,
If tests indicate that there are
no mechanical or electricalfaiIures,replace the ECU.
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35-10SERVICE BRAKES -Anti-lock Braking System Troubleshooting
j CONTINUED FROM PREVIOUS PAGE /After a test drive, use self-diagnosis to
P.35-11.).>
1No trouble codes output and normal
codes are displayed?
NoTrouble codes are output
Yes
All ABS functions are normal.
(Nor are there stored memory of
past trouble code.)put terminals and the di-
agnosis check connector.
If trouble does not re-
appear, watch vehicle
movements until it reap-
pears. (Refer to
P.35-12.)
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SERVICE BRAKES -Anti-lock Braking System Troubleshooting
35-11
Adapter
iarness%f&(MB9913771(Mi3991341)\12FOO57
CHECK USING SELF DIAGNOSIS FUNCTION
(1) With the ignition switch OFF, connect the MUT through the
adapter harness
(MB9913771, turn the ignition ON and
select the ABS system. (The ABS warning light lights up, it
goes into the MUT mode. In the MUT mode, ABS does
not function.)
If it does not go into the MUT mode, check the ECU power
circuit and the harness between the ECU and diagnosis
check terminals.
(2) Read the diagnosis output codes from the ECU memory.
(3) Clear the diagnosis codes once from memory. (Refer to
P.35-12.)If the memory cannot be cleared, the ECU is currently
detecting the trouble and the ABS ECU is in fail safe. If it
can be cleared, the trouble is either temporary or appears
only when driving.
(4) When the trouble codes cannot be cleared, or when the
ABS ECU goes into fail safe during another test drive and
trouble codes are output, check according to trouble code
check charts (E-l-E-6).
DIAGNOSIS CODE CHART
Diagnosis codeCheckReferenceDiagnosis codeCheck
Referencechart namepagechart namepawNo. MUT display lettersor remedyNo. MUT display lettersor remedy
L11FR SNSR. OPEN41FR SOL. VALVE
12FL SNSR. OPEN42FL SOL. VALVEE-4P.35-23E-lP.35-2013RR SNSR. OPEN43REAR SOL. V.
14RL SNSR. OPEN51VALVE RELAYE-5P.35-24
15VEH. SPD. SNSR.E-2P.35-20 52MOTOR RELAYE-6P.35-25
22STOP LAMP SWE-3P.35-2055 CONT. UNITECU-
replacementI
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35-12SERVICE BRAKES -Anti-lock Braking System Troubleshooting
METHOD OF CLEARING DIAGNOSIS
ACTUATOR TEST FUNCTION
CODE MEMORYThe actuator can be forcibly driven in the following
Cautionway by using the MUT.
lWhen servicing is finished, clear the diagno-
sis code memory.NOTEd
lThe actuator test cannot be carried out when the
Trouble codes cannot be cleared from memoryABS ECU system is in fail safe.
when the ABS ECU system is in fail safe. Proceed tol When using forced drive using the MUT, the
diagnosis and repair.vehicle must be stopped.
(1) Clear memory using MUT.
lDuring forced drive using the MUT, forced drive
(No. 7
“DIAG. ERASE” in the actuator test isoperation is stopped when any wheel speed
selected to erase the diaanosis code.)reaches 10 km/h (6 mph).
(2) After clearing, recheck the diagnosis codes, and
check that memory is cleared.
Actuator test specifications
No.MUT display
01FR VALVE A
02
FL VALVE A03
REAR VALVE A04
FR VALVE M
05
FL VALVE M06
REAR VALVE MDrive solenoid
valve and motorDrive pattern
Not used
Solenoid valve and
pump motor for
each HU corres-
ponding channel.

Start of forced drive
End of forced drive
1440588
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.SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-13 'A ABS warning light does not light at all.
iJ[Explanation][Hint]
When it does not light up at all, there is a strongIf other warning lights do not light up either, fuse is
possibility that there is trouble with ABS warningprobably blown.
light or with power to the light.
id
r
f%ER RELAY
110
* ::h=g
6
::5
d
.-2=
?Et0
~
2____--..-
?EI
5fir 4
I
4 -
IGNITIONSWITCH(IG2)m!--
mj:
JSIBLE LINK0tiB
2
L__---------___
0
Lp1%
%2
j:(L-R)dg
6-k
&h+&"..L"Ei SOLENOID1:
G-R
G-R
^ -tl- - D
HH H?bb
IN:IGl)-
59
1
ki@iNATION
iB
ABS-ECU
Kxss-AK-RSGOIA
1 TSB RevisionI

SERVICE BRAKES- Anti-lock Braking System Troubleshooting
Yes
Turn the ignition switch OFF and
check.
4- No
Does voltage between
harness connector terminal
No. 14 and ground indicate
battery voltage?combination meter from
fuse No. 11 is broken.
Yes
ylCircuit in combination meter
is broken.
Is there continuity between combination
meter No. 58 and No 59 terminals7
.rT/“I./ Faulty1 +I[&
r,No ,IAre instrument panel wiring harness
and body wiring harness connected
properly?Connect connectors firmly.
(Check for pins pulled out or
bent, and repair as needed.)
Yes
Broken wire in ECU, valve relay or both
drive circuits. Check both circuits.
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SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-15
ICheck ABS ECU.Remove the ECU connector and
check.Does the voltage between ECU harness
connector terminal No. 25 and ground
indicate battery voltage while the
ignition key is in the “ON” position?
Yes
b Broken wire between ABS
warning light and ECU) Repair harness.
I ABS ECU malfunctionI) Replace ABS ECU.
Is valve relay normal? (Refer to
P.35-62.)Yes+ Valve relay malfunctionb Replace valve relay.
install the valve relay, remove the HU
connector and check.
IDoes voltage between theINO IHU harness\----+I Broken harness wireII1-1 Repair harness.I
Iconnector terminal No. 8 and ground
indicate battery voltage while the
ignition key is in the “ON” position?between ABS warning
light and HU1IYes
Is there continuity between HU harness
4:~~&?$?%$&ndconnector terminal No. 9 and ground?
Is there continuity between HU harness
connector terminals No. 8 and No.
9?
j HU malfunctionI> Replace HU.
Yes
L Connector not connected
securely., Replace connector.I
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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(-
:Et
J’B @
C151
:
E
COMBINATION
METER
-19
7
------____-_---1
2
610 2
~;@lizEFgIIc,
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.
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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.
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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.
J’B 6
[15
Pi9
I58
:127r',L
ALI
Y-3>
B -
::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