1991 MITSUBISHI 3000GT warning light

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.
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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

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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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.
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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.
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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

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
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7
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iMETER
1:I1o‘r_- ----- ‘2 -- ‘Ti----‘%--‘79 -_----- -7 -- “j-+3 -----1
=p!Rq3;
g:W
25
b
ABS-ECU
n=
1 TSB Revision