light MITSUBISHI 3000GT 1991 Owners Manual

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.
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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.
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_
ai.. .
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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).
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SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-37
DABS warning light blinks once after the ignition key is turned to the “ON” position. It
Lilluminates in the “START” position and blinks once again when turned to the “ON” position.
[Explanation]
1 sec. while itharness between the ECU and the warning light, the
light illuminates only when the valve relay is off in
performs a valve relay test. If there is a break in the
the valve relay test, etc.
IGNITIONSWITCH(IG1)I
J/B
F
2
r+im
md
/
L/
COMBINATION
METER
ABS-ECU-____
KK35-KK-It3503In the ignition key “ON”
position, does voltage
between terminal No. 25 and
ground indicate battery
voltage?ABS warninglight and
Yes
Repair harness.
vMalfunction of ABS ECU
+ Replace ABS ECU.
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[Explanation][Hint]
The ABS ECU detects breaks in the wheel speedIn addition to a broken wire/short circuit in the wheel
sensor wire. This trouble code is output if the wheelspeed sensor, also check whether the sensor gap is
speed sensor signal is not input (or short circuited)too large, sensor harness wire is broken, or sensor
or if its output is low when starting to drive or whileharness and body connector are not properly con-
driving.
netted.E-2 When diagnosis code“15 VEH. SPD. SNSR.” is displayed
[Explanation]l Broken sensor harness
This trouble code is output when there is anl Poor connection of connector
abnormality (other than broken wire or short circuit)
NOTEin any of the wheel speed sensor output signals
(1) If contact is poor, check the sensor cable by
while driving.bending and lightly stretching it.
[Hint](2) Except for the case where a fault condition
The following can be considered as the cause of theexists in the system, but the inspection results
wheel speed sensor output abnormality.are normal; if an abnormality cannot be found in
l Distortion of rotor, teeth missingthe sensor. circuit displayed as abnormal, erase
lLow frequency noise interference when sensorthe diagnosis code and turn the ignition switch
harness wire is brokento OFF once, and then test-drive again.
l Noise interference in sensor signalIf the same trouble code is output, replace the
lSensor output signal is below the standard valueABS ECU. If the trouble does not occur any-or amplitude modulation is over the standardmore, the problem is likely to be with the ABS
ECIJ.\value. Using an oscilloscope to measure the
wave shape of the wheel speed sensor output
signal is very effective.
I\-- -.(If the trouble is in the speed sensor circuit, butdis difficult to recreate, it will recur even after the
ABS ECU has been replaced.)35-38
SERVICE BRAKES -Anti-lock Braking System Troubleshooting
E-lWhen the following diagnosis codes are displayed “11 FR SNSR. OPEN”
“12 FL SNSR. OPEN” “13 RR SNSR. OPEN” “14
RL SNSR. OPEN”
d
SPEED SENSOR
FRONTCLH) FRONTGWR!%R(LH) REARmi
m I@m @
If?All110130125ASS-ECI.+tB5
8
8I
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35-40SERVICE BRAKES -Anti-lock Braking System Troubleshooting
E-3When diagnosis code “21 G SNSR.” is displayed
[Explanation]
The ABS-ECU outputs this trouble code in the
following cases.
l G sensor OFF trouble (It is judged that the G
sensor continues to be OFF for more than
approximately 13 seconds except when thevehicle is stopped or when there is stop light
switch input.)
lWhen there is a broken wire or short circuit in
the harness for the G sensor system.
FUSIBLE LINK@
4
pilGGRq;
I4
Bd
pEmg=1
--a
2
__1
It
I,1II1 Ii II II II Ii II II I/ II ;/ II II II II !: II//IIII/.--A
X35-LK-R9505
I
IiNo IfIs G sensor normal? (Refer
to
P.35-92.)Replace G sensor.
I
Yes
Remove the ABS-ECU
connector and check at
the harness connector.
With the ignition key “ON”,
does the voltage between
terminal No. 6 and groundindicate battery voltage?
Repair harness.
”
ABS-ECU malfunctionIJP Replace ABS-ECU.
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SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-41E-4 When diagnosis code“22 STOP LAMP SW” is displayed
ii’ [Explanation][Hint]
The ABS-ECU outputs this trouble code in theIf the stop light operates normal, the harness for the
following cases.stop light switch input circuit is broken or there is a
lStop light switch remains on for more than 15malfunction in the ABS-ECU.
minutes while the ABS is not functioning.
lThe harness wire for the stop light switch may
be open.
L
FUSIBLE,LINK@
J/B
0
I
I
ABS-ECU29
j 1 ) 2 13 14) 5 / 6 17 / 9 j 9 ~10~11~12~13(14~15(161171~9~~'9~0l21~2~3l9~~~6~~~9~~0l31l321U13l35l
KX35-AK-33306
F Check the stop light related
go out
normally?circuit and repair problem
spots.
When the brake pedal is pressed
between connector terminal No.
29 and ground indicate battery
I1 voltage! , Yes /Repair harness.
Is the voltage between No.
1terminal and ground equal to the
battery voltage when measured
wrth resistor connector discon-
nected?
YesRepair harness.
6NoIs resistor resistance 780 to
860 sl?) Replace resistor.
YesIs there continuity between No. 2
FpylReplace ABS-ECU.
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SERVICE BRAKES - Set-vice Adiustment Procedures35-45lUF51F
Pedal
7\ \!4FOO7.
F14511
F14519
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SERVICE ADJUSTMENT PROCEDURES
BRAKE PEDAL INSPECTION AND ADJUSTMENT
1.Measure the brake pedal height as illustrated. If the’brakepedal height is not within the standard value, adjust as
follows.
Standard value (A): 177
- 182 mm (7.0 - 7.2 in.)
(I) Disconnect the stop light switch connector, loosen the
lock nut, and move the stop light switch to a position
where it does not contact the brake pedal arm.
(2) Adjust the brake pedal height by turning the operating
rod with pliers (with the operating. rod lock nut
loosened), until the correct brake pedal height is
obtained.
(3) After screwing in the stop light switch until it contacts
the brake pedal stopper (just before the brake pedal is
caused to move), return the stop light switch
l/2 to 1
turn and secure by tightening the lock nut.
(4) Connect the connector of the stop light switch.
(5) Check to be sure that the stop light is not illuminated
with the brake pedal unpressed.
Reference value (6): 0.5
- 1.0 mm (.02 - .04 in.)
2. On vehicles with automatic transaxle, check the shift-lock
mechanism. (Refer to GROUP 23
- Transaxle Control.)
3. With the engine stopped, depress the brake pedal two or
three times. After eliminating the vacuum in the power
brake booster, press the pedal down by hand, and confirm
that the amount of movement before resistance is met (the
free play) is within the standard value range.
Standard value (C): 3
- 8 mm (.I - .3 in.)
If the free play is less than the standard value, confirm that
the clearance between the stop light switch and brake
pedal is within the standard value.
If the free play exceeds the standard value, it is probably
due to excessive play between the clevis pin and brake
pedal arm. Check for excessive clearance and replace faulty
parts as required.
4.Start the engine, depress the brake pedal with approximate-
ly 500 N (110
Ibs.) of force, and measure the clearance
between the brake pedal and the floorboard.
Standard value (D): 80 mm (3.1 in.) or more
If the clearance is less than the standard value, check for air
trapped in the brake line and for brake fluid leaks. If
necessary, check the brake system mechanism (excessive
shoe clearance due to faulty auto adjuster) and repair faulty
parts as required.~1~1
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35-46SERVICE BRAKES - Service Adjustment Procedures
BRAKE FLUID LEVEL SENSOR CHECK
I
MBSFBAF
Good
k‘14UOO61
When engine is
stoppedNo good
When engine isstarted
14UOO6C)Checkvalve/1. Connect a circuit tester to the brake fluid level sensor.
I
2.Move the float from top to bottom and check for continuity.
3. The brake fluid level sensor is in good condition if there is
‘k&Jno continuity when the float surface is above “A”, and if,there is continuity when the float surface is below “A”.
BRAKE BOOSTER OPERATING INSPECTION
M35FCAOFor simple checking of brake booster operation, carry out the
following tests.
1.Run the engine for one or two minutes, and then stop it.
2. Step on the brake pedal several times with normal
pressure.If the pedal depresses fully the first time but gradually
becomes higher when depressed succeeding times, the
booster is operating properly.
If the pedal height remains unchanged, the booster is
faulty.
3. With the engine stopped, step on the brake pedal several
times with the same pressure to make sure that the pedal
height will not change.
Then step on the brake pedal and start the engine.
If the pedal moves downward slightly, the booster is in
good condition. If there is no change, the booster is faulty.
4.With the engine running, step on the brake pedal and then
stop the engine.
Hold the pedal depressed for 30 seconds. If the pedal
height does not change, the booster is in good condition. If
the pedal rises, the booster is faulty.
If the above three tests are okay, the booster performance can
be determined as good.
If one of the above three tests is not okay at last, the check
valve, vacuum hose, or booster will be faulty.
CHECK VALVE OPERATION CHECKM35FNALWhen checking the check valve, keep the check valve fit in the
vacuum hose.
1. Remove the vacuum hose.
Caution
The check valve is press-fit inside the vacuum hose and
do not remove the check valve from the vacuum hose.1
d~
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35-58SERVICE BRAKES - Service Adjustment Procedures
POINTS IN WAVEFORM MEASUREMENT
Symptom
Too small or zero waveform
amplitudeProbable causes
Faulty wheel speed sensorRemedy
Replace sensor
Incorrect pole piece-to-rotor clearance
Adjust clearance
Waveform amplitude fluctuates
excessively (this is no problem ifAxle hub eccentric or with large runout
Replace hub
the minimum amplitude is
100 mV
or more)
Noisy or disturbed waveformOpen circuit in sensor
Open circuit in harness
Incorrectly mounted wheel speed sensor
Rotor with missing or damaged teethReplace sensor
Correct harness
Mount correctly
Replace rotor
NOTEThe wheel speed sensor cable moves following motion of the front or rear suspension. Therefore, it is likely that it has an
open circuit only when driving on rough roads and it functions normally on ordinary roads. It is, therefore, recommended
to observe sensor output voltage waveform also under special conditions, such as rough road driving,
(ME!991 377)12FOO5i
INSPECTION OF HYDRAULIC UNITINSPECTION BY FEEL
(I) Jack up the vehicle and support the vehicle with rigid racks
placed at the specified jack-up points.
(2) Release the parking brake and determine the drag force
(drag torque) of each wheel by feel.
LJ(3) Set the MUT through the adapter harness (MB991377) as
illustrated.
(4) After confirming that the shift lever or selector lever is in
the neutral position, start the engine.
The ABS warning light lights up, it goes into the MUT mode.
In the MUT mode, ABS does not function.
(5) Operate the MUT to force the actuator to operate (item No.
04, 05, 06).
(6) Turning the wheel manually, check the change of the
braking force when the brake pedal is depressed.
The change should be as shown in the following illustration.
NOTEWhile the ABS is in the fail safe mode, the MUT actuator
test cannot be made.
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