ignition MITSUBISHI 3000GT 1991 Workshop Manual

13-76FUEL SYSTEM - On-vehicle Inspection of MPI Components
IGNITION SWITCH-ST AND INHIBITOR SWITCH <A/T>
lqnition switch (ST)
@ Equipment side
connectorStarter S Control
terminalrelay
f,BL
Engine control unit connector7FUO625
Engine control unit
@ Harness side
connector
7FUO653
OPERATIONl
The ignition switch-ST inputs a high signal to the engine control unit while the engine is cranking. Theengine control unit provides fuel injection control, etc., at engine startup based on this signal.
l
When the ignition switch is set to START, the battery voltage at cranking is applied through the ignitionswitch and inhibitor switch to the engine control unit, which detects that the engine is cranking.
In case the selector lever is in a position other than the P/N range, the battery voltage is not applied to theengine control unit.
l
The inhibitor switch converts the selector lever position (whether it is at the P/N range or at others) into
high/low voltage and inputs it to the engine control unit, which then controls the idle speed control servobased on this signal.
l
The battery voltage in the engine control unit is applied through a resistor to the inhibitor switch. When the
selector lever is set to the P/N range, continuity is produced between the inhibitor switch terminal of the
engine control unit and ground through the starter motor, thereby making the terminal voltage go low.
TROUBLESHOOTING HINTS
If the inhibitor switch harness and individual part check have resulted normal but the inhibitor switch output isabnormal, poorly adjusted control cable is suspected.
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-77INSPECTION
Using Multi-use Tester
LIGNITION SWITCH-ST
FunctionItem No. Data displayCheck conditionEngineNormal rndrcation
Data reading18Switch stateIgnition switch: ON
stopOFF
CrankingONINHIBITOR SWITCH
FunctionItem No. Data displayCheck conditionSelect lever positionNormal indicationData reading 29
Shift
Ignition switch: ONP or NP or Nposition
D.2,L or RD.2.L or RHARNESS INSPECTION
@ Harness sideconnector
OlA0206
2
@ Harness srdeconnectorl
Engine control unit connector:
Connectedl
InhibItor switch connector: Dis-6a
L-J
cl3
connectedl Ignition switch: ON
Repair the
harness.Voltage
(VI@El - El)
OlA0206LII
Engine control
unit harness
side connector
Measure the power supply voltage of
the inhibitor switch.
-lEngine control unit connector:
Disconnectedl
lnhibrtor switch connector: Dis-
connectedl Ignition switch: START
Voltage
(V)
rLlltXK IlIt:Lpower supplycircuit.
Measure the inhibitor switch terminalinput voltage.
Measure the input voltage of enginecontrol unit.lEngine control unrt connector:DisconnectedlFer;it;r switch connector: Con-
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FUEL SYSTEM - On-vehicle lnwection of MPI ComDonents
2Measure the power supply voltage ofthe vehicle speed sensor.
@ Harness sidel Connector: Dlsconnectedl Ignition switch: ON
8)
6FU1265l Connector: Disconnected
SENSOR INSPECTIONRefer to GROUP 54
- Meters and Gauges.
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FUEL SYSTEM - On-vehicle Inspection of MPI Components
AIR CONDITIONER POWER RELAY
L
FunctionItem No. Data display
Data reading49Air condi-tioner relay
stateCheck conditionEngine: Idling after
warm-up
HARNESS INSPECTIONAir conditioner switch
Normal indication
OFFOFF (compressor
clutch non-activa-
tion)
ONON (compressorclutch activation)
’ I
unit harness
side connector
7FUO695
Measure the power supply voltage of
the air conditioner circuit.l
Air conditioner switch: ONlEngine control unit connector:
Disconnectedl Ignition switch: ON
l
Dual air conditioner switch: ONVoltage
(V)IM
ASTOP
Check the airconditioner
circuit.
AIR CONDITIONER INSPECTIONRefer to GROUP 55
- Service Adjustment Procedures.
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13-84FUEL SYSTEM - 0n-vehicle Inspection of MPI Components
DETONATION SENSOR
Engine control unitN
/J-l
@ Equipment side58: :connectorI I
t- =I IL .J531 5:2::
i SEL1208j
@ Harness side
connector7FU1075
Engine control unit connector
7FUO653
OPERATION
The detonation sensor generates a voltage proportional to the magnitude of cylinder block vibration due to
knocking and inputs it to the engine control unit. Based on this signal, the engine control unit provides retardcontrol of the ignition timing.
TROUBLESHOOTING HINTS
When knocking occurs while driving under high-load conditions, the following problems are suspected inaddition to the detonation sensor itself.
(1) Inappropriate ignition plug heat range
(2) Inappropriate gasoline(3) Incorrectly adjusted reference ignition timing
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13-88FUEL SYSTEM - On-vehicle Inspection of MPI Components
MUFFLER MODE CHANGEOVER SWITCH <Turbo>
Engine control unit
r
@ Equipment sideconnector3
-Muffler
modeOFF changeover
ONswitch
2
r
7FU1053
OPERATIONlIf the operator turns the muffler mode changeover switch to ON or OFF position, this is converted to
high/low voltage to be sent to the engine control unit. Receiving this signal, the engine control unit
performs the dual mode (TOUR/SPORT mode) muffler control.
lThe output terminal of the muffler mode changeover switch has battery voltage applied to it from the
engine control unit through the resistor inside the unit. Place the muffler-mode changeover switch to the ‘LJj
ON posrtton, and the muffler mode changeover switch circuit will be closed to short the voltage applied
output terminal to the ground.. Accordingly, the output voltage of the muffler mode changeover switchchanges from high to low.
INSPECTION
Using Multi-use Tester
FunctionItem No. Data displayCheck conditionMuffler mode changeover Normal displayswitch condition
Data list35Switch
conditionIgnition switch: ONTurn to TOUR mode
Turn to SPORT modeON
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FUEL SYSTEM - 0n-vehicleInspection of MPI Components13-89 ~
HARNESS INSPECTION
1
connector
*7FU10547FU105:
ii
Measure the power supply voltage.
l Connector: Disconnectedl Ignition switch: ON
Voltage
(V)
sv
i+
Repair the
harness.
@pJ- Ilosi)
Check for continuity of the ground
circuit.
l Connector: Disconnected
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-91
HARNESS INSPECTION
i‘@ Harness side
:
7
6FU1241
Measure the power supply voltage ofthe air intake control valve position
sensor.l Connector: Disconnected
l Ignition switch: ON
@ Hannector
=7FUO824
7FUO825
Check for continuity of the groundcircuit.l Connector: Disconnected
f---Y -
Measure the terminal voltage.l Connector: Disconnected
l Ignition switch: ON
T
Repair the
harness.TSB Revision

FUEL SYSTEM- On-vehicle Inspection of MPI Components13-93INSPECTION
Using Multi-Use Tester
FunctionItem No. Data displayCheck conditionEngine stateStandard valueData reading 43
SensorEngine: Warmed up700 rpm (Idle)100°C (212°F) or less
temperatureEngine is maintained in-
a constant state for3,500 rpm120°C (248°F) or more
2 minutes or moreHARNESS INSPECTION
connector
2-..-I
@ Harness side
connector
m2 1
4
1
Measure the power supply voltage.l Connector: Disconnected
l Ignition switch: ON
Voltage
(V)4.3
- 4.7Repair the
harness.
(@I@ - q I
Check for continuity of the groundcircuit.
l Connector: Disconnected
I
Repair the
harness.@@J-m,
SENSOR INSPECTION
Refer to GROUP 17 - Exhaust Gas Recirculation (EGR) System.TSB Revision

13-96FUEL SYSTEM - 0n-vehicle Inspection of MPI Components
HARNESS INSPECTION
rMeasure the power supply voltage ofthe oxygen sensor.l Connector: Disconnected
l Ignition switch: ON
Voltage
(V)sv
Repair the
harness.
(@m - Con-trol relay)
- 7FUO827
e oxygen sensor.
Disconnected
connectorl Connector: Disconnected
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