MITSUBISHI 3000GT 1991 Service Manual

SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-39
Check flow connected with wheel
speed sensorNOTECheck speed sensor harness and connector connection
and then observe with oscilloscope. (Refer to
P.35-57.)No ,
Is the resistance value of the wheel
speed sensor part normal?
Standard value: 0.8 - 1.2 kR
z Malfunction of wheel speed
sensor
Yes
,I”
/
LY14N0127
L14N0181
1Yes
-NoCheck the output of each
wheel speed sensor with an
oscilloscope, including the
waveform. (Refer to
P.35-57.)Is the output voltage for each
wheel speed sensor over
the standard value and is
the waveform normal?
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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.
visionI

35-42SERVICE BRAKES -Anti-lock Braking System Troubleshooting
E-5When diagnosis codes “41 FR SOL. VALVE”,
“42 FL SOL. VALVE” or “43 VALVE DRIFT”
are displayed.
‘LJ[Explanation]
The ABS-ECU normally monitors the solenoid valve
drive circuit.
If no current flows in the solenoid even if the ECU
turns the solenoid ON or if it continues to flow even
when turned OFF, the ECU determines thesolenoid coil wire is broken/short-circuited or the
harness is broken/short-circuited, and then these
trouble codes are output.
ABS-ECU controls the solenoid valve current and if
the current value of the solenoid valves differs from
j:
z!d
9
E6T
mA9f#;NATIOM
I-N----_---____IGNITION
SWITCH(IG2)Fw
"50
fm!EaqG-R
?,I G-RI
X35-AK-K3507each other in the same mode, solenoid valve drift
error is produced and the ABS-ECU goes into the
failsafe mode.
1No
In the resistance value forthe solenoid valve withinthe range of the standard
values?
Standard value: 1.1 - 1.3 R
Yes
”
) Replace HU.
Connect HU 1 OP connector,
\ ci;;;;;;;t EC,U connector,)
Yes
+The harness wire for the
solenoid valve circuit
whose resistance value is
outside the range of the
standard value is brokenor short circuited.
Repair harness.
1 Malfunction of ABS-ECU4 Replace ABS-ECU.I IIII1
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SERVICE. BRAKES -Anti-lock Braking System Troubleshooting35-43
E-6When diagnosis code “51 VALVE RELAY” is displayed
I
L[Explanation]
When the ignition switch is turned ON, the ABS
normal. In addition, normally it monitors whether or
ECU switches the valve relay OFF and ON for annot there is power in the valve power monitor line
initial check, compares the voltage of the signal tosince the valve relay is normally ON. If the supply of
the valve relay and valve power monitor line voltagepower to the valve power monitor line is inter-
to check whether the valve relay operation is
rupted, this trouble code will be output.
b
L
IGNlTIONSWITCH(IG1)
-I--
iz
=pi7TEaq
dI
6
7
Ed
COMBINATION
METER
--;Gm1 I 11
I /I
--- --
710 4Ii+
mI%
~d10 2
--- -- -?
ii3Dz62 27
iE b
1112j31a15(6/71618/10(11112113/14/15j16/17(18118~20~21~2~3~4~5~~~2@~~~0~31~2~3~~~35
KX35-AK-K3503
r-TSB I
( ;;reove;d ch; the>
4.IWhen the valve relay is checked,
are the following conditions
found?
No. 85
- No. 86: Resrstance
value 60 - 120 IINo. 30-No. 87a: Continuity
No. 30 - No. 87: No continuity
When batterv voltaoe IS aooliedbetween terminalsho. 86 and
No. 85.
No. 30
- No. 87: Contrnurty
No. 30 - No. 87a: No continurtyNo
I1-----+Valve relay malfunction
+l
IReplace valve relay.I
Yes
&I/ No1IWith the ignition key “ON”,
does the voltage between the
connector terminal No. 52 and
ground indicate battery voltage?
Yes
Connect the HU harness and
\ remove the ECU connector.
+II NnrIground Indicate battery voltage.
Replace ABS
ECIJ.
vision

35-44SERVICE BRAKES -Anti-lock Braking System Troubleshooting
E-7When diagnosis code “52 MOTOR RELAY” is displayed
[Explanation]
The ABS ECU outputs this trouble code for the
motor relay and motor in the following cases.
l When the motor relay does not function
lWhen there is trouble with the motor itself and it
does not revolve
lWhen the motor ground is disconnected and the
motor does not revolve
l When the motor continues to revolve
[Hint]
If there is motor operation noise during MUT forced
drive mode, there is a broken or short circuited
motor monitor wire.
FUSIBLE LINKa
=
::
s* m’ IL% Q7
plGizq”+-103 1
----..-___I _-
3%ECU2526L--h h
Th v-sTIII
14 ’
+---I
i”
’-ll21314 15 16 17 16 ~8~10)11~12~13~14~15~16~17~16~li1Q~0~1~~23~4~*6~2?~E~Q~30~1~2~33~~~5J
X35-AK-R3500during MUT forced drive mode?
Remove the motor relay.
I
1 ;;pa4r&&rness between 1
5Remove the motor relay and
check resistance values.
No. 85
- No. 86: Resistance
value 30 - 60 fiNo. 30 - No. 87: No continuity
Battery voltage is applied
kotw8esfn terminals No. 85 and
No. 30
- No. 87: ContinuityReplace motor relay.
1Yes
L
+I, NoIIIs pump motor ground connected
normally?Connect ground wire.
I
YesInstall motor relay and remove
HU connector.
@Vyiground indicate battery voltage?
I Yes
IConnect the HU connector
and remove the ECU connectorRepair harness.
J- No
Is resistance between bodyP Malfunction of harness
connector terminal No. 2
Lrbetween HU and ECU
and No. 26 30 - 60 a?
ItNc-11 I<
r 1 Repair harness.;~~:;$$a$?%dABS ECU malfunction
> Replace 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
I
I
I
I
I

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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SERVICE BRAKES - Service Adjustment Procedures35-47Valve
Spring
Pressure
w-wPressure
,*’ISplit point
,*“”,’,’,’I’
,’,’
output
br.,’
,’pressure
Input pressure14U005E
2.Check the operation of the check valve by using a vacuum
pump.Vacuum pump connection
Connection at the brake
booster side @
Connection at the intake
manifold side @created and held.
created.
Caution
If the check valve is defective, replace it as an assembly
unit together with the vacuum hose.
PROPORTIONING VALVE FUNCTION TESTMOBFKAK1. Connect two pressure gauges, one each to the input side
and output side of the proportioning valve, as shown.
2. Air bleed the brake line and the pressure gauge.
3. While gradually depressing the brake pedal, make the
following measurements and check to be sure that the
measured values are within the allowable range.
(1) Output pressure begins to drop relative to input
pressure (split point).
Standard value: 3.75
- 4.25 MPa (533 -- 604 psi)
(2) Output fluid pressure when input fluid pressure is 8.0MPa (1,138 psi)
Standard value: 5.23
- 5.73 MPa (744 - 815 psi)
(3)
C$txrt pressure difference between left and right brake
Limit: 0.4
MPa (57 psi)
4. If the measured pressures are not within the permissible
ranges, replace the proportioning valve.
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35-48SERVICE BRAKES - Service Adjustment Procedures
BLEEDINGCautionM35FYAOUse the specified brake fluid. Avoid using a mixture of the
specified brake fluid and other fluid.
Specified brake fluid: Conforming to DOT314POO3C
1
14A045
When new
When wornWear
indicator
Lrakedisc
indicatorBrake
disc
14FOO4CBLEEDING THE MASTER CYLINDER
If the master cylinder is empty of brake fluid, bleed the cylinder
as follows.
(1) Fill the reserve tank with brake fluid.
(2) Depress and hold the brake pedal.
(3) Let your fellow worker plug the master cylinder outlet with
finger.
(4) Keeping the condition (3), release the brake pedal.
(5) Repeat steps
(2) to (4) three to four times while filling the
master cylinder with brake fluid.
BLEEDING THE BRAKE PIPE LINE
Bleed the brake pipe line with the engine running in the order
shown in the illustration.
Caution
When adding brake fluid on vehicles with ABS, be sure to
fit the filter to the reserve tank.
FRONT DISC BRAKE PAD CHECK AND REPLACE-
MENTM35FQAG
NOTEThe brake pads have wear indicators that contact the brake disc
when the brake pad thickness becomes 2 mm
(.079 in.), and
emit a squealing sound to warn the driver.
&ionI