Mitsubishi Galant 9G. Manual — part 417
TROUBLESHOOTING GUIDELINES
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GENERAL
00-6
TROUBLESHOOTING GUIDELINES
M1001008800340
VERIFY THE COMPLAINT
• Make sure the customer's complaint and the ser-
vice writer's work order description are under-
stood before starting work.
• Make sure you understand the correct operation
of the system. Read the service manual descrip-
tion to verify normal system operation.
• Operate the system to see the symptoms. Look
for other symptoms that were not reported by the
customer, or on the work order, that may be
related to the problem.
DETERMINE POSSIBLE CAUSES
Compare the confirmed symptoms to the diagnostic
symptom indexes to find the right diagnosis proce-
dure.
If the confirmed symptoms cannot be found on any
symptom index, determine other possible causes.
• Analyze the system diagrams and list all possible
causes for the problem symptoms.
• Rank all these possible causes in order of proba-
bility, based on how much of the system they
cover, how likely they are to be the cause, and
how easy they will be to check. Be sure to take
experience into account. Consider the causes of
similar problems seen in the past. The list of
causes should be ranked in order from general to
specific, from most-likely to least-likely, and from
easy-to-check to hard-to-check.
FIND THE PROBLEM
After the symptoms have been confirmed, and prob-
able causes have been identified, the next step is to
make step-by-step checks of the suspected system
components, junctions, and links in logical order.
Use the diagnostic procedures in the service manual
whenever possible. Follow these procedures care-
fully to avoid missing an important step in the diagno-
sis sequence. It might be the skipped step that leads
to the solution of the problem.
If the service manual doesn't have step-by-step pro-
cedures to help diagnose the problem, make a series
of checks based on the ranked list of probable
causes. Troubleshooting checks should be made in
the order that the list of causes was ranked:
• general to specific
• most-likely to least-likely
• easy-to-check to hard-to-check
REPAIR THE PROBLEM
When the step-by-step troubleshooting checks find a
fault, perform the proper repairs. Make sure to fix the
root cause of the problem, not just the symptom. Just
fixing the symptom, without fixing the root cause, will
cause the symptom to eventually return.
VERIFY THE REPAIR
After repairs are made, recheck the operation of the
system to confirm that the problem is eliminated. Be
sure to check the system thoroughly. Sometimes
new problems are revealed after repairs have been
made.
HOW TO USE TROUBLESHOOTING/INSPECTION SERVICE POINTS
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GENERAL
00-7
HOW TO USE TROUBLESHOOTING/INSPECTION SERVICE
POINTS
TROUBLESHOOTING CONTENTS
M1001013300062
CAUTION
• During diagnosis, a DTC code associated with
other system may be set when the ignition
switch is turned on with connector(s) discon-
nected. On completion, confirm all systems
for DTC code(s). If DTC code(s) are set, erase
them all.
• When the MUT-III detects a diagnostic trouble
code, its display informs users whether a
mechanical problem currently exists ("current
trouble") or whether it existed before but nor-
mal operation has been restored ("past trou-
ble"). However, if an MFI, TPMS or SRS
airbag-related DTC is set, "Active DTC/Stored
DTC" is not displayed. In this case, follow the
diagnosis procedure for current trouble.
• If a trouble, detected in a CAN communica-
tion-capable system, can be reproduced,
diagnose the CAN bus lines (Refer to GROUP
54C, Can Bus Line Diagnostics Chart
Troubleshooting of electronic control systems for
which the scan tool can be used follows the basic
outline described below. Even in systems for which
the scan tool cannot be used, part of these systems
still follow this outline.
1. STANDARD FLOW OF DIAGNOSTIC
TROUBLESHOOTING
Troubleshooting strategy is shown in each group.
2. SYSTEM OPERATION AND SYMPTOM
VERIFICATION TESTS
If verification of the symptom(s) is difficult, proce-
dures for checking operation and verifying symptoms
are shown.
3. DIAGNOSTIC FUNCTION
The following trouble code diagnoses are shown.
• How to read diagnostic trouble codes
• How to erase diagnostic trouble codes
• Input inspection service points
4. DIAGNOSTIC TROUBLE CODE CHART
If the scan tool displays a diagnostic trouble code,
find the applicable inspection procedure according to
this chart.
5. SYMPTOM CHART
If there are symptoms, even though the scan tools
show that no DTCs are set, inspection procedures
for each symptom will be found by using this chart.
6. DIAGNOSTIC TROUBLE CODE
PROCEDURES
Indicates the inspection procedures corresponding to
each diagnostic trouble code. (Refer to
7. SYMPTOM PROCEDURES
Indicates the inspection procedures corresponding to
each symptom listed in the Symptom Chart (Refer to
).
8. SERVICE DATA REFERENCE TABLE
Inspection items and normal judgment values have
been provided in this chart as reference information.
9. CHECK AT ECU TERMINALS
Terminal numbers for the ECU connectors, inspec-
tion items, and standard values have been provided
in this chart as reference information.
.
TERMINAL VOLTAGE CHECKS
1. Connect a needle-nosed wire probe to a voltmeter
probe.
CAUTION
Short-circuiting the positive (+) probe between a
connector terminal and ground could damage
the vehicle wiring, the sensor, the ECU, or all
three. Use care to prevent this!
2. Insert the needle-nosed wire probe into each of
the ECU connector terminals from the wire side,
and measure the voltage while referring to the
check chart.
NOTE: Measure voltage with the ECU connectors
connected.
You may find it convenient to pull out the ECU to
make it easier to reach the connector terminals.
Checks don't have to be carried out in the order
given in the chart.
3. If voltage readings differ from normal condition
values, check related sensors, actuators, and
wiring. Replace or repair as needed.
HOW TO USE TROUBLESHOOTING/INSPECTION SERVICE POINTS
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GENERAL
00-8
4. After repair or replacement, recheck with the
voltmeter to confirm that the repair has corrected
the problem.
.
TERMINAL RESISTANCE AND
CONTINUITY CHECKS
1. Turn the ignition switch to the "LOCK" (OFF)
position.
2. Disconnect the ECU connector.
CAUTION
If resistance and continuity checks are per-
formed on the wrong terminals, damage to the
vehicle wiring, sensors, ECU, and/or ohmmeter
may occur. Use care to prevent this!
3. Measure the resistance and check for continuity
between the terminals of the ECU harness-side
connector while referring to the check chart.
NOTE: Checks don't have to be carried out in the
order given in the chart.
4. If the ohmmeter shows any deviation from the
Normal Condition value, check the corresponding
sensor, actuator and related electrical wiring, then
repair or replace.
5. After repair or replacement, recheck with the
ohmmeter to confirm that the repair has corrected
the problem.
10. INSPECTION PROCEDURES USING
AN OSCILLOSCOPE
When there are inspection procedures using an
oscilloscope, these are listed.
HOW TO USE TROUBLESHOOTING/INSPECTION SERVICE POINTS
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GENERAL
00-9
HOW TO USE THE INSPECTION PROCEDURES
M1001013500066
The causes of many of the problems occurring in electric circuitry are generally the connectors, components,
the ECU, and the harnesses between connectors, in that order. These inspection procedures follow this
order. They first try to discover a problem with a connector or a defective component.
ACX00861AE
(1) Relevant circuit(s) of the component which
the DTC indicates are described.
(3) Shows the location of the connector(s) from
the circuit(s) above.
(4) Explains about the operation principle of the
component or its relevant parts in that circuit.
B-48(B)
(2) For connector color, refer to GROUP 80A,
How to read configuration diagrams.
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