How to diagnose MITSUBISHI 3000GT 1994 2.G Workshop Manual

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i Service Manual
3000~l-
1992-l 996
Volume
2
Electrical
FOREWORD
i
L
This Service Manual has been prepared with the latest service information available at the time of
publication. It is subdivided into various group
categories and each section contains diagnossis,
disassembly, repair, and installation procedures
along with complete specifications and tightening
references. Use of this manual will aid in properly
performing any servicing necessary to maintain or
restore the high levels of performance and reliability
designed into these outstanding vehicles.
@
A
.
.,
WESUF’FORTVOLUNTARY TECHNICIAN
CERTiFiCATlON THROUGH
National lnaltute forAUTOMOTIV ESERVICEEXCELLENC E
Mitsubishi Motors Corporation reserves the right to make changesin design or to make additions to or improvements in its products withou\
timposing any obligations upon itself to install them on its productspreviously manufactured.
L
--
GROUP / SECTION INDEX
General. . . . . . . . . . . . . . . . . . . . . . . .
Fusible Link, Fuse an d IOD or
Storage Connector Locatio n
. . . . . . . . . .w
Inspection Terminal Location . . . . . . . . .
Grounding Location . . . . . . . . . . . . . . . . . .w
m
Relay Location . . . . . . . . . . . . . . . . . . . . . -m
Sensor Locatio
n. . . . . . . . . . . . . -. . . . . . .w
Control Unit Location . . . . . . . . . . . . . . . . .m
Solenoid, Solenoid Valve Location . . . . .d
Diode Location . . . . . . . . . . . . . . -. . . . . . .w
Junction Block . . . . . . . . . . . . . . . . . . . . . . .II
Centralized Junction . . . . . . . . . #. . . . . . .w
Harness Connector Inspectio n. I . . . . . .w
How to Diagnose . . . . . . . . . . . . . -. . . . . . .
111
Configuration Diagrams . . . . . . . . . . . - . .m;
Circuit Diagrams . . . ..*.............
Engine Electrical ...............
ChassisElectrical
............ .
Alphabetical Index .............
NOTE:
For information concerning all compo-
nents other than the electrical system and
on-vehicle service procedures for engines
and transmissions, refer to Volume 1
“Chassis & Body” of this paired Service
Manual.
For overhaul procedures of engines or
transmission, refer to the separately is-
sued Engine Service Manual or Manual/
Automatic Transmission Service Manual.
@ 1995 Mitsubishi Motors CorporationReprinted in USA

Downloaded from www.Manualslib.com manuals search engine GENERAL - How to Diagnose27
HOW TO DIAGNOSE
L;The most important point in troubleshooting is to determine “Probable Causes”. Once the probable causes
are determined, parts to be checked can be limited to those associated with such probable causes. Thereforeunnecessary checks can be eliminated. The determination of the probable causes must be based
ona theory and be supported by facts and must not be based on intuition only.
TROUBLESHOOTING STEPSIf an attempt is made to solve a problem without going through correct steps for troubleshooting, the
problem symptoms could become more complicated, resulting in failure to determine the causes correctly
and making incorrect repairs. The four steps below should be followed in troubleshooting.
I i
,;zirvation of Problem Symp-Determination of Probable
CausesI
Observe the symptom carefully.
Check if there are also other problems.
In determining the probable causes, it is necessary to check
the wiring diagram to understand the circuit as a system.
Knowledge of switches, relays and other parts is necessary
for accurate determination. The causes of similar problems
in the past must be taken into account.
After the problems are corrected, be sure to check that
the system operates correctly. Also, check that new prob-
lems have not been caused by the repair.
INFORMATION FOR DIAGNOSIS
Troubleshooting is carriedout by making step by step
is found. Always go through
what check is to be made where
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This manual contains the cable diagrams as well as the individual circuit drawings, operational explanations,
and troubleshooting hints for each component required to facilitate the task of troubleshooting. The information
is compiled in the following manner:
(1) Cable diagrams show the connector positions, etc., on the actual vehicle as well as the harness path.(2) Circuit drawings show the configuration of the circuit with all switches in their normal positions.
(3) Operational explanations include. circuit drawings of voltage flow when the switch is operated and
how the component operates in reaction.
(4) Troubleshooting hints include numerous examples of problems which might occur, traced backwardin a common-sense manner to the origin of the trouble.
Problems whose origins may not be found in this manner are pursued through the various system
circuits.
NOTE
Components of MFI, ETACS, ECS, etc. with ECU do not include 3 and 4 above. For this information,
refer to a manual which includes details of these components.
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Downloaded from www.Manualslib.com manuals search engine GENERAL - How to Diagnose
Changeover k&bZ1680224
Z1680225
INSPECTION1. Visual and aural checks
Check relay operation, blower motor rotation, light illumina-d
tion, etc. visually or aurally. The flow of current is invisiblebut can be checked by the operation of the parts.
2. Simple checks
For example, if a headlight does not come on and a faultyfuse or poor grounding is suspected, replace the fuse
with a new one or ground the light to the body by a jumper
wire to determine which part is responsible for the problem.3. Checking with instruments
Use an appropriate instrument in an adequate range andread the indication correctly. You must have sufficient
knowledge and experience to handle instruments correctly.
INSPECTION INSTRUMENTS
In inspection, make use of the following instruments.1. Test lights
A test light consists of a 12 V bulb and lead wires. It
is used to check voltages or short circuits.
2. Self-power test light
A self-power test light consists of a bulb, battery and lead
wires connected in series. It is used to check continuity
or grounding.
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Downloaded from www.Manualslib.com manuals search engine GENERAL - How to Diagnose293. Jumper wire
A jumper wire is used to close an open circuit. Never
use one to connect a power supply directly to a load.
Z16602274. Voltmeter
A voltmeter is used to measure the circuit voltage. Normally,the positive (red lead) probe is applied to the point of
voltage measurement and the negative (black lead) probeto the body ground.
5. Ohmmeter
An ohmmeter is used to check continuity or measure resis-
tance of a switch or coil. If the measuring range has been
changed, the zero point must be adjusted before measure-
ment.
CHECKING SWITCHES
In a circuit diagram, a switch is represented by a symbol andin the idle state.
1. Normal open or normal close switch
Switches are classified into those which make the circuit
open and those which make the circuit closed when off.
INormal open (NO) typeIOFF
/4-
1X
t
Current does not flow
16X0690
ON
1
a
ia
Current flows
16X0691
00000401
Normal close (NC) type
i===ONOFF
1
/4-
1X
Current does not flow16X0690
00000402
a
III
Current flows
16X0691
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Downloaded from www.Manualslib.com manuals search engine 30GENERAL - How to Diagnose
5432
1
18AO253
10W80800000403
Coil
Iron
Cover
Spring
Iron
core
- ContZt
21680231
(NO) type
Energized state1Normal op6
Deenergized state
--
nKilX
Current does not flow
lSXO804
!
Current flows10x0095000004042. SWITCH CONNECTION
This figure illustrates a complex switch. The continuity
between terminals at each position is as indicated in the
table below.4th stage
CHECKING RELAYS1. When current flows through the coil of a relay, its core
is magnetized to attract the iron piece, closing (ON) the
contact at the tip of the iron piece. When the coil current
is turned off, the iron piece is made to return to its original
position by a spring, opening the contact (OFF).
2.By using a relay, a heavy current can be turned on and
off by a switch of small capacity. For example, in the circuit
shown here, when the switch is turned on (closed), current
flows to the coil of the relay. Then, its contact is turned
on (closed) and the light comes on. The current flowingat this time to the switch is the relay coil current only
and is very small.3. The relays may be classified into the normal open type
and the normal close type by their contact construction.
NOTE
The deenergized state means that no current is flowing
through the coil and the energized state means that current
is flowing through the coil.
JI
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Downloaded from www.Manualslib.com manuals search engine iGENERAL
- How to Diagnose31
Normal close (NC) type
Deenergized stateEnergized state
Current does not flow
Z1680235
State of fuse blown due to overcurrent
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I21680237
State of fuse blown due to thermal fatigue
Z1660236When a normal close type relay as illustrated here is
checked, there should be continuity between terminals
(1) and (2) and between terminals 3 and 4 when the relay
is deenergized, and the continuity should be lost betweenterminals 3 and 4 when the battery voltage is applied
to the terminals
1 and 2. A relay can be checked in this
manner and it cannot be determined if a relay is okay
or faulty by checking its state only when it is deenergized
(or energized),
CHECKING FUSESA blade type fuse has test taps provided to allow checking
of the fuse itself without removing it from the fuse block. Thefuse is okay if the test light comes on when its one lead is
connected to the test taps (one at a time) and the other lead
is grounded. (Change the ignition switch position adequatelyso that the fuse circuit becomes live.)
CAUTIONS IN EVENT OF BLOWN FUSE
When a fuse is blown, there are two probable causes as follows:One is that it is blown due to flow of current exceeding its
rating.The other is that it is blown due to repeated on/off current
flowing through it. Which of the two causes is responsible
can be easily determined by visual check as described below.(1) Fuse blown due to current exceeding rating
The illustration shows the state of a fuse blown due to
this cause. In this case, do not replace the fuse with a
new one hastily since a current heavy enough to blow
the fuse has flowed through it. First, check the circuit
for shorting and check for abnormal electric parts. Only
after the correction of such shorting or parts, fuse of the
same capacity should be used as a replacement. Never
use a fuse of larger capacity than the one that has blown.
If such a fuse is used, electric parts or wirings could be
damaged before the fuse blows in the event an overcurrent
occurs again.(2) Fuse blown due to repeated current on/off
The illustration shows the state of a fuse blown due to
repeated current on/off. Normally, this type of problem
occurs after fairly long period of use and hence is less
frequent than the above type. In this case, you may simplyreplace with a new fuse of the same capacity.
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iGENERAL
- How to Diagnose33
Power supply
Fuse
’ i
ON (2),----c//ISwitch
I
Motor
Z16AO260
GENERAL ELECTRICAL SYSTEM CHECKSA circuit consists of the power supply, switch, relay, load
ground, etc. There are various methods to check a
circui;
including an overall check, voltage check, short circuit checkand continuity check. Each of these methods is briefly de-
scribed in the following.
1. VOLTAGE CHECK
(1) Ground one lead wire of the test light. If a voltmeter
is used instead of the test light, ground the groundingside lead wire.
(2) Connect the other lead wire of the test light to the
power side terminal of the switch connector. The test
light should come on or the voltmeter should indicate
a voltage.
(3) Then, connect the test light or voltmeter to the motor
connector. The test light should not come on, or the
voltmeter should indicate no voltage. When the switch
is turned on in this state, the test light should come
on, or the voltmeter should indicate a voltage, with
motor starting to run.(4) The circuit illustrated here is normal but if there is
any problem such as the motor failing to run, check
voltages beginning at the connector nearest to themotor until the faulty part is identified.
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Downloaded from www.Manualslib.com manuals search engine GENERAL - How to Diagnose2. SHORT-CIRCUITS CHECK
A blown fuse indicates that a circuit is shorted. The circuit responsible can be determined by the
following procedures.Remove the blown fuse and connect a test light in its place
(Switch is in the OFF position)
Test light comes on
+
NO
1 Short circuit between fuse block and switch (A)Turn on the switch
(Test light comes on but the illumination light does not come on)ItDisconnect the illumination light connector
I+Test light remains on
iNO
Short circuit between the illumination light connector and illumina-tion liaht ((3
Short circuit between the switch and illumination
light connector (B)A
Power supply
(Remove the fuse.)
1OFF
gi
location
Switch
a
Illuminationfight
16.4om2
BPower supply
Fuse block(Remove
the fuse.)
* Disconnect the load
iii
Illumination
light
T16Aom
13. CONTINUITY CHECK
Self powertest light
(or ohmmeter)
Z16AO269
C
Power supply
Test
lightFuse block
(Remove the fuse.)
Switch
Disconnect the load
ii
Short-circuit- location
Illumination
light
16Alncd?00000741
(1) When the switch is in the OFF position, the self powertest light should come on or the ohmmeter should
read 0 ohm only when the terminals 1 and 2 are inter-
connected.
(2) When the switch is in the ON position, the self powertest light should come on or the ohmmeter should
read 0 ohm only when the terminals 3 and 4 are inter-
connected.
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