1991 MITSUBISHI 3000GT check engine light

ELECTRONIC CONTROL SUSPENSION (ECS) - Troubleshooting 33B-11
I I7
Anti-squat control only stops.III
L,
I
Using MUT, check service data onthrottle position sensor. Good?
Yes
rCheck by entering simulated vehicle speed from MUT to
simulate anti-squat control. (Refer to P.33B-16.) Good?!
1 Good1 ) Replace ECS control unit. 1
I
1I II
NoDoes check engine light illuminate?>Is continuity provided between No. 2 terminal of throttleposition sensor and No. 59 terminal of ECS controlunityII
Yes
i
Correct harness.
1Check throttle position sensor. (Refer to P.33B-20.) Good?III1
connector and check harness con-nector with ignition switch at ON.
No. 1 terminal voltage and continuityNo
Is
between No. 4 terminal and groundcontinuity provided across the following areas?
up to specification? (Sensor powerthrottle position sensor and engine control unit
No. 1 and 61 terminals
supply and ground)
No. 4 and 72 terminalsStandards:
INo. 1 terminal5 V
YesNo. 4 terminal
Continuity provided
Yes-1 1 Correct harnei:
”
Replace throttle position sensor.TSB Revision

SERVICE BRAKES -Anti-lock Braking System Troubleshooting35-7
ANTI-LOCK BRAKING SYSTEM TROUBLESHOOTlilGPARTICULAR PHENOMENA OF THE
LANTI-LOCK BRAKING SYSTEMModels equipped with the anti-lock braking system
(ABS) may exhibit one or more of the following
phenomena from time to time, but none of these
are abnormal.
(1) A pulsing feeling in the brake pedal, or vibration
of the body or the steering wheel, when the
anti-lock braking system is activated by sudden
braking or by braking on a slippery road surface.
.9ctually, this phenomenon is an indication that
the anti-lock braking system is functioning nor-
mally.(2) When the vehicle speed reaches approximately
6 km/h (4 mph) after the engine is started and
the vehicle starts off (for the first time), a
whining motor noise may be heard from the
engine compartment if the vehicle is traveling in
a quiet place, but this noise is simply the result
of a self-check being made of the anti-lock
braking system operation.
TROUBLESHOOTING METHODSProblems related to the anti-lock braking system
(ABS) can be classified into two general categories:
problems in the electrical system and those in the
Lhydraulic system.For problems in the electrical system, the
self-diagnosis function is built into the electronic control
unit (E.C.U.) causing the ABS warning light to
illuminate as a warning to the driver. In this instance,
checks can be made by using the multi-use tester
and oscilloscope.
Problems in the hydraulic system (poor braking,
etc.) can be located in the same way as for ordinary
brakes. There is, however, the necessity to check to
determine whether the problem is related to ordin-
ary brake components or to the components related
to the ABS. To make this check, use the multi-use
tester.
HOW TO USE THE TROUBLESHOOTING
FLOW CHART(1) Using the flow chart, check the ABS warning
light light-up sequence. Read the diagnosis
codes and check the condition of braking opera-
tion.
(2) Following the check chart listed in the remedy
column, perform the checks. There are [Explana-
tion] and [Hint] in each check chart. Refer to
them when troubleshooting.
NOTEECU: Electronic control unit
HU: Hydraulic unit
MUT: Multi-use tester
1 TSB Revision

35-8SERVICE BRAKES -Anti-lock Braking System Troubleshooting
TROUBLESHOOTING (ABS - FWD)Confirm condition in the following way and diagnosis accordingly.
Does the ABS warning light illuminate as described
(2) With the ignition key in the “START” position,
below up to the time the engine starts?power to the ABS ECU is interrupted and the
(1) When the ignition key is turned to the “ON”ABS warning light remains lit because the valve
position, the ABS ECU causes the ABS warningrelay is OFF.
light to flash twice in about one second (during
(3) When the ignition key is returned from the
which the valve relay self check is made) and“START” position to the “ON” position, the
then causes it to go out.ABS warning light flashes twice in about one
second (during which. the valve relay self check
-is made again) and then goes out.
ABS warning
ONlightII
-I
keyACC,
LO!: +--14A0589
Yes>CONTINUED ON NEXT PAGE
No
”
weenABS warning
1 TSB Revision

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.
bvision

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

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 - Set-vice Adiustment Procedures35-45lUF51F
Pedal
7\ \!4FOO7.
F14511
F14519
TSB Revision-_.1
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~
TSB Revision