1991 MITSUBISHI 3000GT engine

13-82FUEL SYSTEM - On-vehicle Inspection of MPI Components
AIR CONDITIONER SWITCH AND POWER RELAY
\
*I \\-- \
Air conditronerAir conditioner
control unitAir conditioner
compressor lock
controllerr
Engine control unit
Dual pressureswitch
M13YRAA2
b1IFF
Air conditioner
compressor
Engine control
unit connector
7FUO966
7FUO653
OPERATION
lThe air conditioner switch applies the battery voltage to the engine control unit when the air conditioner is
turned on.
lWhen the air conditioner ON signal is input, the engine control unit drives the idle speed control servo and
turns ON the power transistor. As a result, the air conditioner power relay coil is energized to turn on therelay switch, which activates the air compressor magnetic clutch.
TROUBLESHOOTING HINTS
If the air compressor magnet clutch is not activated when the air conditioner switch is turned on during idling,faulty air conditioner control system is suspected.
INSPECTION
Using Multi-use Tester
AIR CONDITIONER SWITCH
Function1 Item No. 1 Data display 1Check condition) Air conditioner switch 1 Normal indication IData reading 28
Switch stateEngine: Idling (airOFFOFFcompressor to be running
when air conditionerONONswitch is ON)\k”JTSB Revision

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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13-86FUEL SYSTEM - On-vehicle Inspection of MPI Components
ELECTRICAL LOAD SWITCH16FO29;
Tail-lightrelayDefog.wrelaystoplight
t;1
switch
ti* . .
Engine control unit connector
Engine
control
unit7FUO653
7FUO688OPERATION
lThe electrical load switch inputs ON/OFF state of the switch of equipment that consumes much powerduring idling, namely, equipment with a large electrical load, to the engine control unit. Based on this
signal, the engine control unit controls the idle-speed control servo.
l
When the switch of equipment with a large electrical load is turned ON, the battery voltage is applied tothe engine control unit to indicate that the equipment switch is turned ON.,
LJINSPECTION
Using Multi-use Tester
Function
Data reading
I
tem No. Data display
-I-
33Switchstate
Check condition
Equipment stateNormal display
$;ration of equipment:L$ing;Atch only:OFF + ON-3
1 TSB Revision

FUEL SYSTEM - On-vehicle InsDection of MPI ComDonents
/
idHARNESS INSPECTION
Engine control
unit harness
side connector7FUO689
side connector7FuO689
PU
Engine control
unit harness
side connectorT7FUO689
Measure the input voltage of engineIcontrol unit.
lEngine control unit connector:
Disconnectedl Lighting switch: ON
(Tail light relay ON)
Measure the input voltage of enginecontrol unit.
lEngine control unit connector:
Disconnectedl Defogger switch: ON
(Defogger relay ON)Voltage
(V)
Isv
cl3
Check circuit
related to de-
fogger relay
Measure the input voltage of enginecontrol unit.
lEngine control unit connector:
Disconnected
l Brake pedal: Depressed(Stop light switch ON)
Check circuitTSB Revision

13-88FUEL SYSTEM - On-vehicle Inspection of MPI Components
MUFFLER MODE CHANGEOVER SWITCH
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
OFFTSB Revision

13-90FUEL SYSTEM - On-vehicle Inspection of MPI Components
INDUCTION CONTROL VALVE POSITION SENSOR
Variable induction control se
(DC motor)(with built-In induction
control valve position sensor)
Vakiable induction control servo (DC motor)
[Induction control valve
1
@ Equipment side
connector
Variable
inductloncontrol servo
connector
7FUO968
OPERATIONl The induction control valve position sensor detects the induction control valve opening degree and
converts it into a pulse signal to be input into the engine control unit, which provides valve opening andclosing control based on this signal.
l
The induction control valve position sensor is supplied with 5 V power from the engine control unit and is
grounded to the engine control unit. A voltage of 5 V from the engine control unit is impressed to the two
output terminals of the induction control valve position sensor. By opening and closing the circuit between
the output terminal and ground, the induction control valve position sensor generates the pulse signal.TSB Revision

FUEL SYSTEM - On-vehicle Inspection of MPI Components
EGR TEMPERATURE SENSOR M13YZh82
EGR tem0erature senso
7FUlOlO
@ Equipment s,de EGR temperature sensor
connectorII@ Harness side
Enginecontrol
unit
I Iconnector
7FU1013I
Temperature1621008
OPERATIONl
The EGR temperature sensor converts the temperature of EGR gas downstream from the EGR valve to
voltage and inputs it to the engine control unit. The engine control unit judges the condition of the EGR bythis signal. If there is abnormal condition, the engine warning light is turned on to notify the driver.
l
Five volt power supply in the engine control unit is applied to the EGR temperature sensor through the
resistance in the unit. This power supply further passes through the EGR temperature sensor, which is a
kind of a resistor, and is grounded at the engine control unit. The resistance of the EGR temperature
sensor is characterized by a decrease in resistance with an increase of EGR temperature due to increasein quantity of EGR.
l EGR temperature sensor terminal voltage increases or decreases with EGR temperature sensor
resistance. Therefore, EGR temperature sensor terminal voltage changes with EGR gas temperature. Thehigher the EGR gas temperature, the lower the EGR temperature sensor terminal voltage.
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