ECU MITSUBISHI 3000GT 1991 Owners Manual

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
TSB Revision1

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

SERVICE BRAKES -Anti-lock Braking System Troubleshooting
MUT
I/(MB991 341)
\03A0211
DIAGNOSIS CODE CHART
I I21G SNSR.IE-3
[ 22 1 STOP LAMPSW 1E-4
CHECK USING SELF DIAGNOSIS FUNCTION
(1) With the ignition switch OFF, connect the MUT through the
adapter harness (MB991377). 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.35-30.)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-7).
Reference
we -1 ;+EiT;
I I41FR SOL. VALVEI
P.35-381 ;; / ;;tS;L;;;E/ E-5
I I51VALVE RELAY
P.35-38 1 52 1 MOTOR RELAY)E-7
si 55 / ‘ONT. UNlT/ replaEcCeUment
Reference
iwe
P.35-42
P.35-43
P.35-44
-
1 TSB RtivisionI

35-30SERVICE BRAKES -Anti-lock Braking System Troubleshooting
METHOD OF CLEARING DIAGNOSIS
ACTUATOR TEST FUNCTION
CODE MEMORYCautionThe actuator can be forcibly driven in the following
way by using the MUT.
lWhen servicing is finished, clear the diagno-
sis code memoryNOTElThe actuator test cannot be carried out when the
Trouble codes cannot be cleared from memoryABS ECU system is in fail safe mode.
when the ABS-ECU system is in fail safe mode.
Proceed to diagnosis and repair.l When using forced drive using the MUT, the
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 diagnosis code.)reaches 10 km/h (6 mph).
(2) After clearing, recheck the diagnosis codes, and
check that memory is .cleared.
Actuator test specifications
Not usedStart of forced drive
1 TSB Revision

SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-31
L’A ABS warning light does not light at all.
[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.
FUSIBLE LINEI
L--L5--
i
IGNITIONSWITCH(IG2)IGNITIONSWITCH(IG1)
(L-R)-' .3
G-RI
7
!
m59COMBINATION
iMETER
1:I1o‘r_- ----- ‘2 -- ‘Ti----‘%--‘79 -_----- -7 -- “j-+3 -----1
=p!Rq3;
g:W
25
b
ABS-ECU
n=
1 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
:ml-
I2a-----11 g:I aI7
:I1
-_307a
-
I-=_-. -----------1
P
Y
4 a:&
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

SERVICE BRAKES -Anti-lock Braking System Troubleshooting
35-35
IGNITIONSWITCH(IG2)
R&RRELAY
DIODE
KX35-AK-R35028PREVIOUS PAGE
With the ignition key in the
“ON” position, does voltage
between ECU connector
terminal No. 18 and ground
indicate the battery voltage?
Is there continuity between
body harness terminals No. 9
and No. 34, and ground?
Repair harness.
vNoIs there continuity between-body harness connector ter-diagnosis inspection
minals No. 23 and No. 24,terminal and ABS ECU
and diagnosis inspection ter-
minals No. 4 & No. 1 O?Yes
”Malfunction of ABS ECU
Replace ABS ECU.
TSB Revision

35-36\
SERVICE BRAKES -‘\Anti-lock Braking System Troubleshooting
CABS warning light does not illuminate when the ignition key is in the “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
IG, power source which is
not turned off even in the “START” position.
Consequently, in the “START” position, power is off
LJand 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.
EfiE-
9B
wIGNSW1--
J/BF
COMBINATIONMETER
G-R 11 G-
IN;IGl)
ITSB IRemove the hydraulic
unit (HU) connector andcheck.
Yes
c-No -Is there continuity between-> Broken line between HUbody connector terminal No. 9
and body ground
and ground?
-No 7Is there continuity between> Valve relay malfunction orHU connector terminal No. 8
break in HU harness wire
and terminal No. 9?
YesYes
&
Replace valve relay.I
1
HU harness malfunctionj Replace HU.
NOTEWhen performing the check marked *, note polarity of the diode
(refer to the circuit diagram).
visionI