check engine MITSUBISHI 3000GT 1991 Workshop Manual

13-52FUEL SYSTEM - 0
n-vehicle Inspection of MPI Components
-i8
@ Harness side
connector
Check for an open-circuit, or a short-circuit to ground, between the controlrelay and the engine control unit.l
Control relay connector: Discon-
nectedl
Engine control unit connector:
Disconnected
Engine controlunit harness
side connector
7FUO475g
/Check for continuity between thecontrol relay and the control relay (for
fuel pump).l
Control relay connector: Discon-
nectedl
Control relay (for fuel pump) con-nector: Disconnected
zonnector8 Harness side
connector
/
7FUO96:
T
Check for continuity of the ground
circuit.l Connector: Disconnected
!
Repair the
harness.
@pJ-Ground)
7FUO476
Check for an open-circuit, or a short-circuit to ground, between the controlrelay (for fuel pump) and the fuel
pump.l
Control relay (for fuel pump)connector: DisconnectedlFuel pump connector: Discon-nectedRepair the
harness.
(@@-@lTJ)
@I Harness sidtconnector@Harness side
connector
I7FUO964
CONTROL RELAY INSPECTIONRefer to
P.13-43.TSB Revision
1

FUEL SYSTEM - On-vehicle Inspection of MPI Components13-55
INSPECTIONUsing Multi-use Tester

Function
Data readingtern No. Data display
12Sensor airvolume(frequency)
Check conditionEngine stateStandard value
l Engine coolant tem-
700 rpm (Idle)25-50 Hzperature: 80 to 95°C
(176 to 205°F)2,000 rpm70-IOOHzl Lights and accessories:OFFRacingFrequency increasesl Transaxle: Neutralwith racing(P range for vehiclewith AIT)l Steering wheel: Neutral
NOTEWhen the vehicle is new [within initial operation of about 500 km (300 miles)], the air flow sensor output frequency maybe about 10% higher.

Function
Data listItem No. Data displayCheck conditionsEngine conditionsStandard value
34Reset signall Engine warm up700 rpm (Idle)ON
condition2,000 rpmOFF
L;
FunctionItem No. Data display
Data list37Volumetric
efficiencyCheck conditionEngine stateStandard valuel Engine coolant tem-700 rpm (Idle)20-35%
perature: 80 to 95°C
(176 to 205°F)
l Lights, electric cooling2,000 rpm15-30%
fan and accessory opera-tion: OFFl Transaxle: NeutralRacingFrequency increases
(P range for vehiclewith racingwith &T)
l Steering wheel: Neutral
Using Oscilloscope(1) Run the engine at idle speed.
(2) Connect the probe to the oscilloscope pick-up point as
shown in the circuit diagram, and check the waveform.
Regular waveform
03A0203
TSB Revision

13-56FUEL SYSTEM - 0
n-vehicle Inspection of MPI Components
HARNESS INSPECTION
--barness side
connector
*7FUO656
connector
7FUO6574
?
@ Harness sideEngine c&lconnector
unit harness
side connector
I -
1
m
!h 4.7Fuo745u
Measure the power supply voltage.l Connector: Disconnected
l Ignition switch: ON
Voltage
(V)
eoair the
check the
control relay.
Measure the terminal voltage.l Connector: Disconnected
l Ignition switch: ON
Check for continuity of the ground
circuit.l Connector: Disconnected
Repair the
harness.
@El - I@)
Check for continuity between the air
flow sensor and the engine control
unit.l Air flow sensor connector: Dis-f
connected10l Engine control unit connector:
‘L-/Disconnected. .Rr.annir th(
t
I ‘“yu’3harness.
TSB Revision

13-58FUEL SYSTEM - On-vehicle Inspection of MPI Components
INSPECTION
Using Multi-use Tester
FunctionItem No. Data displayCheck conditionIntake air temperatureStandard valued
Data reading13Sensorignition switch: ON orAt -20°C (-4°F)-20°C
temperatureengine running
At 0°C (32°F)0°C
At 20°C (68°F)20°C
At 40°C (104°F)40°C
At 80°C (176°F)80°C
HARNESS INSPECTION7FUO657
I
connector
7FUO6607FUO661
ITSB I
Check for continuity of the groundcircuit.l Connector: Disconnected
Repair the
harness.,
(@I3 - q ,
Measure the power supply voltage.l Connector: Disconnected
l Ignition switch: ON
Voltage
(V)4.5
- 4.9Repair the
harness.
@@J-@)
SENSOR INSPECTION
(1) Disconnect the air flow sensor connectors.
(2) Measure resistance between terminals @ and
@.
ITemperature [“C (“F)]IResistance (kfl)
I0 (32)I6.0
I20 (681I2.7
wisionI
d

FUEL SYSTEM - On-vehicle Inspection of MPI Components13-61
TROUBLESHOOTING HINTS
Hint 1 : If the barometric pressure sensor is faulty, poor driveability is caused at high altitude, in particular.
L
Hint 2: If the pressure indication of the barometric pressure sensor drops significantly during high speeddriving, check the air cleaner for clogging.
INSPECTIONUsing Multi-use Tester
Function
Data readingItem No.’ Data display
25
Check conditionAltitudeStandard value
Sensor
pressureIgnition switch: ON
At 0 m (0 ft.)760 mmHg
At 600 m (1,969 ft.)
710 mmHg
I/At 1,200 m (3,937 ft.)1660 mmHgI
At 1,800 m (5.906 ft.)610 mmHg
HARNESS INSPECTION
II
L
7FUO657
7FUO66:
Check for continuity of the ground
circuit.l Connector: Disconnected
Repair the
harness.
&@I - q ,
Measure the power supply voltage ofthe barometric pressure sensor.l Connector: Disconnected
l Ignition switch: ON
Voltaqe (V)4.8
- 5.2Repair theharness.
KgpJ-pJ,
Engine contraunit harnessside connects
Check for an open-circuit, or a short-circuit to ground between the enginecontrol unit and the barometric pres-,Y---,A
sure sensor.l
Air flow sensor connector: Dis-(OK) -+ kTOA
connectedlEngine control unit connector:
Disconnected
--I
Repair the
harness.

Jg
7FUO666
1 TSB Revision

id
LFUEL SYSTEM
- On-vehicle Inspection of MPI Components13-63
INSPECTIONUsing Multi-use Tester
LFunctionItem No. Data displayCheck condition
Coolant temperatureStandard valueData reading 21
SensorIgnition switch: ON or
At -20°C (-4°F)-20°C
temperatureengine operatingAt 0°C (32°F)0°C
HARNESS INSPECTION
Check for continuity of the groundcircuit.l Connector: Disconnected
Repair the---+ harness.

7FUO6682
Measure the power supply voltage.l Connector: Disconnected
@ Harness sidel Ignition switch: ON
7FUO669TSB Revision

13-64FUEL SYSTEM - 0
n-vehicle Inspection of MPI Components
7FUO670
Apply sealant
7FUO67’SENSOR INSPECTION
(1) Remove engine coolant temperature sensor from the
intake manifold.(2) With temperature sensing portion of engine coolant
temperature sensor immersed in hot water, check resis-
tance.
Temperature
“C (“F)Resistance (kCI)
0 (32)5.8
20 (68)2.4
40 (104)1.1
80 (176)0.3
(3) If the resistance deviates from the standard value greatly,
replace the sensor.
INSTALLATION
(1) Apply sealant to threaded portion.
Specified sealant: 3M NUT locking Part No. 4171 or
equivalent
(2) Install engine coolant temperature sensor and tighten it to
specified torque..Sensor tightening torque: 30 Nm (22
ft.lbs.)
(3) Fasten harness connectors securely.TSB Revision

FUEL SYSTEM - On-vehicle Inspection of MPI Components13-65
i
1
THROTTLE POSITION SENSORM13YJAC
Maximum
Throttle shaft
turning angle
162481
Minlmum
@ Unleaded
Equipment side
connectorThrottle positron sensor
I
@ Harness side
connector
Ii
SEL14001
Engine control unit ,
I
Engine control unit connector
7FUO672
7FUO653
OPERATIONl
The throttle position sensor converts the throttle position opening into a voltage and inputs it to the enginecontrol unit, which then controls the fuel injection based on the input signal.
l
The 5 V power in the engine control unit is supplied to the throttle position sensor. Through the resistor inthe sensor, it is grounded in the engine control unit.
l
As the throttle valve shaft rotates from the idle position to Wide open position, the resistance between the
variable resistor terminal of the throttle position sensor and the ground terminal increases. As a result, thevoltage at the throttle position sensor variable resistance terminal also increases.
TROUBLESHOOTING HINTS
Hint 1: The throttle position sensor signal is more important in the control of automatic transaxle than in theengine control. Shifting shock and other troubles will be caused if this sensor is faulty.
Hint 2: If the output voltage of the throttle position sensor is out of specification, adjust the sensor and
check the voltage again. If there is an evidence of disturbed idle position switch (fixed SAS) setting,adjust the idle position switch (fixed SAS).
1 TSB Revision

13-66FUEL SYSTEM - 0n-vehicle Inspection of MPI Components
INSPECTIONUsing Multi-use Tester
FunctionItem No. Data displayCheck conditionThrottle valveStandard value‘d
Data reading14SensorIgnition switch: left ONvoltagefor 15 seconds or moreAt idle position300-1.000 mV
Open slowly
Increases withvalve opening
Open widely4.500-5.500 mV
HARNESS INSPECTIONl Connector: Disconnected
l
lgnrtion switch: ON
l Connector: Disconnected
connector
I
Engine controlCheck for an open-circuit, or a short-
unit harnesscircuit to ground between the engine
side connectorcontrol unit and the throttle positionsensor.
Throttle position sensor connec-
tor: Disconnected
Engine control unit connector:
DisconnectedRepair theB-3 harness.
km-8)
-z =6FU1243
[ TSB Revision

13-68FUEL SYSTEM - On-vehicle Inspection of MPI Components
IDLE POSITION SWITCHMlBYKAD
Throttle positionse(Idle position switch
2
/bz----;-p
b+i
Throttle shaft turning angle D’20g2
i
Engine control unitI
@ Harness side
connectorIdle position,
@ Equipment side switchconnector
Throttle position
sensor connector
5EL1400
7FUO674
OPERATIONl The idle position switch senses whether the accelerator pedal is depressed or not, converts it into
high/low voltage and inputs the voltage to the engine control unit, which then controls the idle speed
control servo based on the input signal.
lThe voltage in the engine control unit is applied to the idle position switch through a resistor. When the
accelerator pedal is released, the idle position switch is turned on to conduct the voltage to ground. Thiscauses the idle position switch terminal voltage to go low from high.
TROUBLESHOOTING HINTS
If the idle position switch harness and individual part check results are normal but the idle position switchoutput is abnormal, the following troubles are suspected.
’(1) Poorly adjusted accelerator cable or auto-cruise control cable
(2) Poorly adjusted idle position switch (fixed SAS)
INSPECTIONUsing Multi-use Tester
FunctionItem No. Data displayCheck conditionThrottle valveNormal indicationData reading 26
Switch state
Ignition switch: ONON(check by operatingAt idle position
accelerator pedalOpen a littleOFF-J
repeatedly)TSB Revision