Mitsubishi 380. Manual - part 307

TROUBLESHOOTING GUIDELINES

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

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 DIAGNOSTIC TOOL (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 normal operation has 
been restored (“past trouble”). However, if an 
MPI, 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 

P.54C-15

 or 

P.54C-15

).

Troubleshooting of electronic control systems for 
which the MUT -III can be used follows the basic out-
line described below. Even in systems for which the 
MUT-III 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 MUT-III displays a diagnostic trouble code, find 
the applicable inspection procedure according to this 
chart.

5. SYMPTOM CHART

If there are symptoms, even though the MUT-III 
shows 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 

P.00-9

).

7. SYMPTOM PROCEDURES

Indicates the inspection procedures corresponding to 
each symptom listed in the Symptom Chart (Refer to 

P.00-9

).

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. Use correct tool to check each pin location on the 

ENGINE-ECU Check harnes MB992044 and 
measure with voltmeter.

CAUTION

Short-circuiting the positive (+) test 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 correct terminal tool into each of the 

ENGINE-ECU check harness connector 
terminals, 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 connect the ENGINE-ECU check 
harness.

HOW TO USE TROUBLESHOOTING/INSPECTION SERVICE POINTS

GENERAL

00-8

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.

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 ENGIN-ECU check 
harness MB992044 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

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.

00DB075A

(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.

(2) For connector color, refer to GROUP 80A,
      How to read configuration diagrams.

DTC P0202: Injector Circuit Malfunction - Cylinder 2.

CAUTION

If DTC P0202 has been set, TCL related DTC 
U1120 is also set. After P0202 has been diag-
nosed, don't forget to erase DTC U1120.

CIRCUIT OPERATION

• Refer to DTC P0300 - Random/Multiple Misfire- 

P.13B-481

 and Misfire Cylinder 2- 

P.13B-487

.

• The injector power is supplied from the MFI relay 

(terminal No. 4).

• The ECU controls the injector by turning the 

power transistor in the ECU "ON" and "OFF".

TROUBLESHOOTING HINTS (The most 
likely causes for this code to be set are:)

• No. 2 cylinder injector failed.

• Open or shorted to ground No.2 cylinder injector 

circuit.

• Shorted to battery, No.2 cylinder injector circuit.

• Harness or connector damage.

• Refer to component locations GROUP-

70

• Refer to configuration diagrams GROUP-

80

• Refer to circuit diagrams GROUP-

90

AK303102

CONNECTOR: B-30

B-30 (GR)

AB

1

2

3

4

1

2

3

4

1

2

3

4

1

2

3

4

AK303014

CONNECTOR: B-17X

MFI RELAY

MFI RELAY

FRONT OF VEHICLE

B-17X

AB

16DB400A

COVER

ENGINE

CONTROL

UNIT

AIR

CLEANER

(1) Relevant circuit(s) and

     location(s) of the

     component are described

     in these reference links.