cruise control MITSUBISHI 3000GT 1991 User Guide

13-162CRUISE CONTROL SYSTEM - Troubleshooting
Trouble symptomProbable causeCheck chart No.
Remedy
Cannot accelerate or resume speedOpen or short circuit in
No. 2by using the RESUME switch.RESUME switch circuit inReplace the control switch
control switch
Vacuum pump assemblyNo. 5circuit poor contactRepair the harness or
replace the vacuum pump
Malfunction of thevacuum pump assembly
(including air leaks
from negative pressurepassage)assembly.
Malfunction of the ECU-Replace the ECU.
Even when CANCEL switch is set toON, cruise control is not canceled
Open or short circuit
in CANCEL switchIf the input check
Replace the control switch
(Cruise control, however, iscode No. 27 indicatescircuit in control switch
canceled when brake pedal isa malfunction.
depressed.)No. 2
Malfunction of the ECU-Replace the ECU
The cruise control system can be set
Malfunction of theNo. 4while traveling at a vehicle speedvehicle-speed sensorRepair the vehicle speed
of less than 40 km/h (25 mph), or
circuitsensor system, or replace
there is no automatic cancellationthe part.
at that speed.Malfunction of thespeedometer cable orthe speedometer drive
gear
Malfunction of the ECU
-Replace the ECU.
The cruise control indicator light
No. 3
of the combination meter does notDamaged or disconnectedbulb of indicator lightRepair the harness or
illuminate. (But cruise controlreplace the light bulb.
system is normal)Harness damaged or
disconnected
Malfunction of the ECU
-Replace the ECU.
Cruise control ON indicator light
No. 3
does not come on. (However, cruiseBurned-out indicator lightbulbRepair the harness or
control is functional.)replace the main switch.
Open or short circuit in
harness
Malfunction of control functionby
ON/OFF switching of ELC 4 AA
accelerator switch.
(Non-operation of damper clutch,
2nd gear hold, etc.)
Overdrive is not canceled during
fixed speed driving
No shift to overdrive during
manual driving.
Malfunction of circuitrelated to acceleratorswitch OFF function
Malfunction of the ECU
Malfunction of circuit
related to overdrive
cancellation, or mal-
function of ECU
No. IO
No. 11Repair the harness or
replace the part.
Repair the harness or
replace the part.
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CRUISE CONTROL SYSTEM - Troubleshooting13-163CHECK CHART
it l/Inspection of control unit power supply circuit
L;
,/
id
CRUISE#fi$ROL
0
SWITCH
“71
TROUBLESHOOTING HINTSECU terminal voltage
DESCRIPTION OF OPERATIONThe power is supplied through the ignition switch
(IG,) and cruise control main switch to the control
unit.
1. When the cruise control main switch is set to
ON with the ignition switch at ON, the current
from switch
S, flows through relay Ry, in the
switch. Accordingly, the contact of relay
Ry, is
closed and the power is supplied to the control
unit.
2. When the main switch is released, it automati-
cally returns to the neutral position. Since the
current from switch
S2 flows to relay Ry,, the
contact of relay Ry, remains closed.
3.When the main switch is set to OFF, current to
relay
Ry, is interrupted. This opens the contact
of relay
Ry, to stop the power supply to the
control unit. When the switch is released, it
automatically returns to the neutral position, but
relay Ry, stays in the OFF state.
4. When the ignition switch is set to OFF while
relay Ry, in the main switch is ON, relay
Ry, is
forced to the OFF state just like when the main
switch is set to OFF. Even if the ignition switch
is set to ON again, relay
Ry, stays in the OFF
state until the main switch is set to ON.
NOTEThe numbers beside each connector correspond
to those in the section
(P.13-176) “HARNESS
AND COMPONENTS LAYOUT”
TerminalNo.Signal nameCondition
I
TerminalvoltageI
2Control unit power supplyMain switch ON and neutral positionSystem voltage
thereafter
Main switch OFF and neutral positionov
thereafter8, 14
Control unit groundAt all timesov
16Control unit back up power supplyAt all timesSystem voltage
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13-164CRUISE CONTROL SYSTEM - Troubleshooting
2Inspection of control switch circuit
IGNITIONSWITCHtACC)
*X35-AK-R1302r-
._--------
LE- @CONTROL UNIT
TROUBLESHOOTING HINTSECU terminal voltage
DESCRIPTION OF OPERATIONdThe control switch is a switch in which the SET,
RESUME and CANCEL switches are integrated.
Therefore, different resistance values are used for
the individual switches to change the outputs
(voltages) to the control unit. Current flows through
fuse No. @ of J/B and through the control switch to
the control unit.
1. SET switchWhen the cruise control switch is ON, if the SET
switch is set to ON while vehicle speed is within
a range from about 40 to 145 km/h (25 to 90
mph), the vehicle starts cruising at the speed. If
the SET switch is kept at ON during cruise
operation, the vehicle coasts, and starts cruising
at the speed reached when the SET switch is
set to OFF.
2. RESUME switch
Even if cruise operation is canceled, the vehicle
resumes cruising at the speed set before the
cancellation. Both when the main switch is set
to OFF and when the vehicle speed is reduced
to less than 40 km/h (25 mph) , the vehicle will
not resume cruising at the previously set speed
even if the RESUME switch is set to ON. If the
RESUME switch is kept at ON during cruise
LJoperation, the engine accelerates, and the vehi-
cle starts cruising at the speed reached when
the RESUME switch was set to OFF. (However,
when the vehicle speed is raised to more than
145 km/h (90 mph), the vehicle cruises at
approximately 145 km/h {90 mph).
3. CANCEL switch
When the CANCEL switch is set to ON during
cruise operation, the cancel signal is input to the
control unit which internally interrupts the power
supply to the vacuum pump assembly for
cancellation of cruise operation.
18Control switchSignal name
L
Condition
I
Terminalvoltage1
When all switches are OFFIov1
When SET switch is ONI3vI
When RESUME switch is ON
When CANCEL switch is ON6Vd
Systemvoltage
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CRUISE CONTROL SYSTEM - Troubleshooting13-165
I I3Inspection of indicator light circuitI
CRUl
MAIN-!;$ROLIGNITIONSWITCH(IG1)
l-
CRUISE
CONTROL UNIT
Trl
b!XXSS-AK-RI303
DESCRIPTION OF OPERATION1. Cruise control ON (ASC ON) indicator light
Located in the combination meter, it lights as soon as the main switch is set to ON.
2. Cruise control (CRUISE) indicator light
During cruise control operation, transistor
Tr, in the control unit is kept in the ON state to keep the
indicator light on.
TROUBLESHOOTING HINTSECU terminal voltage
TerminalNo.Signal nameCondition
I
Terminal
voltage
I
23
I I
fr;se control (CRUISE) indicatorWhen cruise control is activeSystem voltage
When cruise control is inactiveov
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13466CRUISE CONTROL SYSTEM - Troubleshooting
I I4Inspection of vehicle speed sensor circuitI

IGNITIONSWITCH(IG1)
5”
El
CRUISE
CONTROL
3UNIT
cl!AI
g6pl!Ezq@zla
;i
d
“m ;ygmq%q
?
VEHICLE
SPEED
SENSOR
xX35-AR-RI304P
19Y
*
$
&
~E$iJ
0z
L
COMBINATION
METER
KX35-AK-Rl3Yla
DESCRIPTION OF OPERATION
The vehicle speed sensor, mounted in the transmission, delivers pulse signals proportional to the rotational
speed of the transmission output gear (vehicle speed) to the control unit. (Four pulse signals generated per
rotation of the output gear) Since the vehicle speed sensor is of the electronic type, the power is supplied
through the ignition switch (IG,).
The vehicle speed sensor is a reed switch type and is mounted in the speedometer. It sends pulse signals
proportional to the rotational speed of the transmission output gear (vehicle speed) to the control unit. (Four
pulse signals generated per rotation of the output gear)
TROUBLESHOOTING HINTSDiagnosis No. 12 (Automatically canceled)
ECU terminal voltage
1TerminalNo.I19
i
Signal nameCondition
Terminalvoltage
Vehicle speed sensor
Slowly drive forward with SELECT lever0 to
0.6Vat “D” or "1 st Speed”2J &l;;:neg
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LjlI~~
\
J1
l/j,

CRUISE CONTROL SYSTEM - Troubleshooting13-167
I I5Inspection of vacuum pump assemblv drive circuitIIII
id
CRUISE CONTROL
MAIN SWITCH
l-
4-'a
1.1-111.PUMP
@
!52613
12
KK33-AK-R1905
DESCRIPTION OF OPERATIONThe vacuum pump assembly consists of a di-
aphragm type negative pressure pump that is driven
by a DC motor, and two solenoid valves (control
valve and relief valve) and is controlled by the.
control unit as shown in the following table.
When the brake pedal is depressed during cruise
control operation, the power supply to the vacuum
pump assembly is cut off.
TROUBLESHOOTING HINTSDiagnosis No. 11 (Automatically canceled)
ECU terminal voltage
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13-168CRUISE CONTROL SYSTEM - Troubleshooting,I
I 6 IInspection of stop light switch circuitIIIII
FUSIBLE LINK@
IDESCRIPTION OF OPERATIONIJ iWhen the brake pedal is depressed during vehicle
speed control, the cruise control (NC) contact of the
stop light switch is opened to interrupt the power
supply to the vacuum pump assembly for
cancella-tion of vehicle speed control. (Refer to P. 13-I 67.) At
the same time, the stop light (NO) contact is closed.
As a result, a cancel signal is input to the control unit
which internally interrupts the vacuum pump
assembly drive circuit.
TROUBLESHOOTING HINTSECU terminal voltage
Terminal
No.Signal nameConditionTerminal
voltage
15Stop light
switchWhen brake pedal
is depressedSystem
voltage
When brake pedal
is not depressed
OVh
”z15d
El 1’STOP
LIGHT
xx35-AX-R1305
7Inspection of clutch switch circuit
CRUISEc!$;ROLDESCRIPTION OF OPERATIONWhen the clutch pedal is depressed during vehicle
speed control, the contact of the clutch switch is
closed. As a result, a cancel signal is input to the
control unit which internally interrupts the power
supply to the vacuum pump assembly drive circuit
for cancellation of vehicle speed control.
TROUBLESHOOTING HINTSECU terminal voltage
II,Terminal
Signal nameConditionTerminal
No.voltage
1Clutch switchWhen clutch pedalOVis depressed
When clutch pedal System ,
is not depressedvoltage
d
KK35-AK-R130TA
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CRUISE CONTROL SYSTEM - Troubleshooting13-169
8Inspection of inhibitor switch circuit
LDESCRIPTION OF OPERATIONThe inhibitor switch is interlocked with the starter
switch. When the gear selector lever is placed in the
“N” position during vehicle speed control, a cancel
signal is input to the control unit which internally
interrupts the power supply to the vacuum pump
assembly drive circuit for cancellation of vehicle
>
%
‘18@
INHIBITOR
SWITCHspeed.TROUBLESHOOTING HINTSECU terminal voltage
Terminal
Signal nameConditionTerminal
No.voltage
1Inhibitor switchInhibitor switch inov
“N” or “P” position
System
voltage
STARTER=
L;RX%-AK-R1907
9Inspection of throttle position sensor circuit
ENGINE
CONTROL
UNIT
:l:DOHC
*-OFF 01
w2,3' /% *
THROTTLE;;f&;iON
{ml@
CRUISE CONTROL UNITKX.95~AC-R1308
DESCRIPTION OF OPERATIONThe throttle position sensor (with built-in idle switch)
is used for engine control as well as cruise control.
The throttle position sensor sends data to the
control unit, regarding the opening of the accelera-
tor. The idle switch inputs the data to the control
unit on whether or not the accelerator pedal is
operated.
TROUBLESHOOTING HINTSDiagnosis No. 17 (Not automatically canceled)
ECU terminal voltage
Signal nameConditionTerminal
voltageIdle switchWhen accelerator OV
pedal is depressed
When accelerator 4.5
- 5.5V
pedal is not de-
pressed
Throttle position During idle0.48
-sensor0.72V
When fully opened 4.0
- 5.5V
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13-170CRUISE CONTROL SYSTEM - Troubleshooting
10Inspection of circuit associated with accelerator pedal switch OFF function
IGNITlOiiI sw1:
Ind
,277
?IOA-..A-"2Y
.
“3EL
3,"I\-
2
.-----------
E
r
r
g:-1
13--
ii
KH(IG2)
ORi13 : DI
"CLt-t-fi[T
UNIT
DESCRIPTION OF OPERATION‘\JThe accelerator pedal switch is used to detect the
operating state of the accelerator pedal. It is one of
the sensors of the
ELC4A/T automatic transmis-
sion. Since the accelerator pedal is not operated
during vehicle speed control,.the cruise control unit
forces transistor
Tr, into the OFF state, creating the
same state as when the accelerator pedal switch is
placed in the OFF state.
1
$iK&ERATOR
SWITCHH
1
2
-I
CRUISE
CONTROL
UNIT
TROUBLESHOOTING HINTSECU terminal voltage
TerminalNo.Signal name
Condition
3Accelerator pedal switch control
power supplyWhen ignition switch is placed at ON
9Accelerator pedal switchWhen accelerator pedal is depressed
When accelerator pedal is not depressed
System voltage
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CRUISE CONTROL SYSTEM - Troubleshooting13-171
11Inspection of circuits associated with overdrive cancel
!IGNITION
OVER
DRIVE
SWITCH
C2,
SW1
il-
'TCH(IG2)
14
,lO
l-l
CRUISE
tHTRO"
DESCRIPTION OF OPERATIONOn a vehicle with cruise control, the OD switch ON signal is input through the cruise control unit to the
ELC-4AIT control unit.
When the vehicle speed control is in the overdrive mode, if the actual vehicle speed falls more than about 7
km/h (4 mph) below the set vehicle speed, the cruise control unit forces transistor
Tr, into the OFF state. This
cancels the overdrive mode because no OD switch ON signal is input to the
ELC-4PJT control unit.
TROUBLESHOOTING HINTS
ECU terminal
voltage
TerminalSignal nameConditionTerminal
No.voltage
3OD signal control power supplyWhen ignition switch is ONSystem voltage
10ELC-4A/T control unitWhen overdrive mode is activeSystem voltage
When overdrive mode is inactiveov
11OD switchWhen OD switch is ONSystem voltage
When OD switch is OFFov
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