Mitsubishi Grandis. Manual — part 732

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-179

STEP 6. Connector check: C-110 engine-ECU
<M/T> connector or engine-A/T-ECU <A/T>

Q: Is the check result normal?

YES :

Check and repair harness between B-103

EGR valve and C-110 engine-ECU <M/T>
connector or engine-A/T-ECU <A/T>
connector

a. Check harness between B-103

(terminal No. 1) EGR valve and
C-110 (terminal No. 3) engine-ECU
<M/T> connector or engine-A/T-ECU
<A/T> connector

b. Check harness between B-103

(terminal No. 3) EGR valve and
C-110 (terminal No. 12) engine-ECU
<M/T> connector or engine-A/T-ECU
<A/T> connector

c. Check harness between B-103

(terminal No. 4) EGR valve and
C-110 (terminal No. 19) engine-ECU
<M/T> connector or engine-A/T-ECU
<A/T> connector

d. Check harness between B-103

(terminal No. 6) EGR valve and
C-110 (terminal No. 26) engine-ECU
<M/T> connector or engine-A/T-ECU
<A/T> connector

• Check power supply line for

open/short circuit.

NO :

Repair or replace.

AK305618AB

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Connector: C-110

<L.H. drive vehicles>

<R.H. drive vehicles>

C-110 (GR)

C-110 (GR)

Harness side connector

AK300987

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6

AC

Connector: B-103

B-103 (GR)

Harness side connector

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-180

STEP 7. Connector check: C-110 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.

AK305618AB

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Connector: C-110

<L.H. drive vehicles>

<R.H. drive vehicles>

C-110 (GR)

C-110 (GR)

Harness side connector

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-181

STEP 8. Check harness between B-103 EGR
valve and C-110 engine-ECU <M/T> or
engine-A/T-ECU <A/T>.

a. Check harness between B-103 (terminal No. 1)

EGR valve and C-110 (terminal No. 3)
engine-ECU <M/T> connector or
engine-A/T-ECU <A/T> connector

b. Check harness between B-103 (terminal No. 3)

EGR valve and C-110 (terminal No. 12)
engine-ECU <M/T> connector or
engine-A/T-ECU <A/T> connector

c. Check harness between B-103 (terminal No. 4)

EGR valve and C-110 (terminal No. 19)
engine-ECU <M/T> connector or
engine-A/T-ECU <A/T> connector

d. Check harness between B-103 (terminal No. 6)

EGR valve and C-110 (terminal No. 26)
engine-ECU <M/T> connector or
engine-A/T-ECU <A/T> connector

• Check output line for damage.

Q: Are the check results normal?

YES :

Go to Step 9 .

NO :

Repair.

STEP 9. Check harness between B-103 (terminal
No. 2, No. 5) EGR valve connector and B-15X
(terminal No. 1) engine control relay connector.

NOTE: Before checking harness, check intermediate
connector C-116, and repair if necessary.

• Check power supply line for damage.

Q: Is the check result normal?

YES :

Replace engine-ECU <M/T> or

engine-A/T-ECU <A/T>.

NO :

Repair.

AK300987

1

2

3

4

5

6

AC

Connector: B-103

B-103 (GR)

Harness side connector

AK305618AB

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5

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26

27

Connector: C-110

<L.H. drive vehicles>

<R.H. drive vehicles>

C-110 (GR)

C-110 (GR)

Harness side connector

AK300987

1

2

3

4

5

6

AC

Connector: B-103

B-103 (GR)

Harness side connector

AK300967

2

1

3

4

AC

Harness side
connector

B-15X

Connector: B-15X

Relay box’s
triangle marks

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-182

Code No. P0421: Warm Up Catalyst Malfunction (cylinder 1, 4)

FUNCTION

• The signal from the cylinder 1, 4 oxygen sensor

(rear) differs from the cylinder 1, 4 oxygen sensor
(front). That is because the catalytic converter
purifies exhaust gas. When the catalytic
converter has deteriorated, the signal from the
cylinder 1, 4 oxygen sensor (front) becomes
similar to the cylinder 1, 4 oxygen sensor (rear).

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

<A/T> compares the output of the cylinder 1, 4
oxygen sensor signals (front and rear).

TROUBLE JUDGMENT

Check Conditions

• Engine speed is 3,000 r/min or lower.

• The accelerator pedal is open.

• Air flow sensor output is 8 gm/s or higher.

• 3 seconds or more elapsed after the

abovementioned conditions were satisfied.

• Intake air temperature is −10°C or higher after the

engine is started.

• Barometric pressure is 76 kPa or higher.

• Under the closed loop air/fuel ratio control.

• Vehicle speed is 1.5 km/h or higher.

• For 10 seconds per cycle, the engine-ECU

<M/T> or engine-A/T-ECU <A/T> monitors 7
cycles of this condition during the drive cycle.

• Short-term fuel trim is between −25 % or higher

and +25 % or lower.

• The cumulative air flow sensor output is 2,931 g

or higher.

Judgment Criterion

• The cylinder 1, 4 oxygen sensor (rear) signal

frequency divided by cylinder 1, 4 oxygen sensor
(front) signal frequency is 0.8 or more.

PROBABLE CAUSE

• Catalytic converter deteriorated

• Failed cylinder 1, 4 oxygen sensor (front)

• Failed cylinder 1, 4 oxygen sensor (rear)

• Failed engine-ECU <M/T>

• Failed engine-A/T-ECU <A/T>

DIAGNOSIS PROCEDURE

STEP 1. Check for leakage of exhaust emission
from exhaust manifold.

Q: Is the check result normal?

YES :

Go to Step 2 .

NO :

Repair.

STEP 2. MUT-III data list

• Refer to Data List Reference Table

P.13A-363

.

a. Item 11: Cylinder 1, 4 oxygen sensor (front)
b. Item 59: Cylinder 1, 4 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

• Item 11: Cylinder 1, 4 oxygen sensor (front)

OK: 0

− 0.4 and 0.6 − 1.0 volt should alternate

15 times or more within 10 seconds (engine
speed at 2,000 r/min).

Q: Is the check result normal?

YES :

Go to Step 4 .

NO :

Replace the cylinder 1, 4 oxygen sensor
(front).

STEP 4. Replace the cylinder 1, 4 oxygen sensor
(rear).

• After replacing the cylinder 1, 4 oxygen sensor

(rear), re-check the trouble symptoms.

Q: Is the check result normal?

YES :

Check end.

NO :

Go to Step 5 .

STEP 5. Replace the catalytic converter (cylinder
1, 4).

• After replacing the catalytic converter (cylinder 1,

4), re-check the trouble symptoms.

Q: Is the check result normal?

YES :

Replacing engine-ECU <M/T> or

engine-A/T-ECU <A/T>.

NO :

Check end.