Mitsubishi Grandis. Manual - part 700

 

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Mitsubishi Grandis. Manual - part 700

 

 

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-51

FUNCTION

• The engine-ECU <M/T> or engine-A/T-ECU 

<A/T> effects air-fuel ratio feedback control in 
accordance with the signals from the oxygen 
sensor (front).

• If the oxygen sensor (front) has deteriorated, 

corrections will be made by the oxygen sensor 
(rear).

• Diagnosis code P0125 becomes stored in 

memory if a failure is detected in the above 
air/fuel ratio feedback control system.

TROUBLE JUDGMENT

Check Conditions

• The engine coolant temperature approximately 

76

°C or more.

• Within the range of air-fuel ratio feedback 

operation.

• Not in low speed operation.

Judgment Criterion

• The oxygen sensor output voltage is not deviated 

from 0.5 V for 30 seconds.

PROBABLE CAUSE

• Failed oxygen sensor (front)

• Harness damage in oxygen sensor (front) circuit 

or loose connector contact

• Failed oxygen sensor (rear)

NOTE: When the oxygen sensor (front) begins to 
deteriorate, the oxygen sensor output voltage will 
deviate from the voltage when the sensor was new 
(normally 0.5 volt at stoichiometric ratio). This 
deviation will be corrected by the oxygen sensor 
(rear).If the oxygen sensor (rear) responds poorly 
because it has deteriorated, it will improperly correct 
the oxygen sensor (front). Thus, even when closed 
loop control is being effected, the fluctuation of the 
oxygen sensor (front) output voltage decreases, 
without intersecting with 0.5 volt. As a result, there is 
a possibility of diagnosis code P0125 becoming 
registered.

• Failed fuel system

• Failed exhaust system

• Failed engine-ECU <M/T>

• Failed engine-A/T-ECU <A/T>

DIAGNOSIS PROCEDURE

STEP 1. MUT-III diagnosis code

Q: Is any other diagnosis code than P0170 or P0173 

output?

YES : 

Inspection chart for diagnosis code (Refer 

to 

P.13A-20

).

NO : 

Go to Step 2 .

STEP 2.MUT-III data list

• Refer to Data List Reference Table 

P.13A-363

.

a. Item 12: Air flow sensor
b. Item 21: Engine coolant temperature sensor

c. Item 59: Cylinder 1, 4 oxygen sensor (front)

d. Item 69: Cylinder 2, 3 oxygen sensor (rear)

Q: Are the check results normal?

YES : 

 Go to Step 3 .

NO : 

Perform the diagnosis code classified check 
procedure for the sensor that has shown an 
abnormal data valve (Refer to Inspection 
Chart for Diagnosis Code 

P.13A-20

).

STEP 3: MUT-III data list

• Refer to Data List Reference Table 

P.13A-363

.

a. Item 25: Barometric pressure sensor

Q: Are the check results normal?

YES : 

Go to Step 4 .

NO : 

Replace engine-ECU <M/T> or 
engine-A/T-ECU <A/T>.

STEP 4.Check for intake of air from intake hose 
and inlet manifold.

Q: Is the check result normal?

YES : 

 Go to Step 5 .

NO : 

Repair.

STEP 5.Check for leakage of exhaust emission 
from exhaust manifold.

Q: Is the check result normal?

YES : 

Go to Step 6 .

NO : 

Repair.

STEP 6.Check throttle body (throttle valve 
portion) for contamination. 

Q: Is the check result normal?

YES : 

 Go to Step 7 .

NO : 

Clean throttle body (throttle valve portion) 
(Refer to 

P.13A-383

).

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-52

STEP 7. Connector check: B-22 cylinder 1, 4 
oxygen sensor (front) connector, C-113 
engine-ECU <M/T> connector or engine-A/T-ECU 
<A/T> connector.

Q: Is the check result normal?

YES : 

 Go to Step 8 .

NO : 

Repair or replace.

STEP8. Check cylinder 1, 4 oxygen sensor (front) 
itself.

• Check cylinder 1, 4 oxygen sensor (front) itself 

(Refer to 

P.13A-391

).

Q: Is the check result normal?

YES : 

 Go to Step 9 .

NO : 

Replace cylinder 1, 4 oxygen sensor (front).

STEP 9. Check harness between B-22 (terminal 
No. 4) cylinder 1, 4 oxygen sensor (front) 
connector and C-113 (terminal No. 109) 
engine-ECU <M/T> connector or engine-A/T-ECU 
<A/T> connector.

• Check output line for damage.

Q: Is the check result normal?

YES : 

 Go to Step 10 .

NO : 

Repair.

AK300973

1

2

3

4

AB

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ƒRƒlƒNƒ^![

B-24 (

"•)

ƒRƒlƒNƒ^![

ƒRƒlƒNƒ^![: B-24

Harness side
connector

B-22 (GR)

Connector: B-22

Cylinder 1, 4 oxygen
sensor (front)

AC

AK305616AB

Connector: C-113

<L.H. drive vehicles>

<R.H. drive vehicles>

C-113 (GR)

C-113 (GR)

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109

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Harness side connector

AK300973

1

2

3

4

AB

ƒn![ƒlƒX‘¤

ƒRƒlƒNƒ^![

B-24 (

"•)

ƒRƒlƒNƒ^![

ƒRƒlƒNƒ^![: B-24

Harness side
connector

B-22 (GR)

Connector: B-22

Cylinder 1, 4 oxygen
sensor (front)

AC

AK305616AB

Connector: C-113

<L.H. drive vehicles>

<R.H. drive vehicles>

C-113 (GR)

C-113 (GR)

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Harness side connector

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-53

STEP 10. Connector check: B-19 cylinder 2, 3 
oxygen sensor (front) connector, C-113 
engine-ECU <M/T> connector or engine-A/T-ECU 
<A/T> connector.

Q: Is the check result normal?

YES : 

 Go to Step 11 .

NO : 

Repair or replace.

STEP 11. Check cylinder 2, 3 oxygen sensor 
(front) itself.

• Check cylinder 2, 3 oxygen sensor (front) itself 

(Refer to 

P.13A-391

).

Q: Is the check result normal?

YES : 

 Go to Step 12 .

NO : 

Replace cylinder 2, 3 oxygen sensor (front).

AK300976

1

2

3

4

AC

B-19 (GR)

Connector: B-19

Harness side
connector

Cylinder 2, 3 oxygen
sensor (front)

AK305616AB

Connector: C-113

<L.H. drive vehicles>

<R.H. drive vehicles>

C-113 (GR)

C-113 (GR)

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120

Harness side connector

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-54

STEP 12. Check harness between B-19 (terminal 
No. 4) cylinder 2, 3 oxygen sensor (front) 
connector and C-113 (terminal No. 108) 
engine-ECU <M/T> connector or engine-A/T-ECU 
<A/T> connector.

• Check output line for damage.

Q: Is the check result normal?

YES : 

 Go to Step 13 .

NO : 

Repair.

STEP 13. Connector check: Injector connector

a. B-101 (No.1 injector connector)
b. B-102 (No.2 injector connector)

c. B-104 (No.3 injector connector)

d. B-105 (No.4 injector connector)

Q: Is the check result normal?

YES : 

 Go to Step 14 .

NO : 

Repair or replace.

STEP 14. Check injector itself.

• Check Injector itself (Refer to 

P.13A-393

).

Q: Is the check result normal?

YES : 

 Go to Step 15 .

NO : 

Replace injector.

AK300976

1

2

3

4

AC

B-19 (GR)

Connector: B-19

Harness side
connector

Cylinder 2, 3 oxygen
sensor (front)

AK305616AB

Connector: C-113

<L.H. drive vehicles>

<R.H. drive vehicles>

C-113 (GR)

C-113 (GR)

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Harness side connector

AK300978

M

1

2

AG

Harness side connector

Connectors: B-101, B-102, B-104, B-105

B-101 (GR) B-102 (GR)

B-105 (GR)

B-104 (GR)

 

 

 

 

 

 

 

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