Mitsubishi Colt Ralliart. Manual - part 708

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-157

STEP 13. Perform output waveform check at 
A-110 camshaft position sensor connector (using 
an oscilloscope).

• Use the special tool test harness (MB991709) to 

connect the connector, and measure at the 
pick-up harness.

• Engine: Idling

• Transmission: Neutral

• Voltage between terminal No. 2 and earth.

OK: Waveforms should be displayed on 
Inspection procedure using an oscilloscope 
(Refer to 

P.13B-352

), its maximum value 

should be 4.8 V or more, and its minimum 
valve should be 0.6 V or less with no noise in 
waveform.

Q: Is the check result normal?

YES : 

Go to Step 9.

NO : 

Go to Step 14.

STEP 14. Connector check: B-106 engine control 
relay connector

Q: Is the check result normal?

YES : 

Go to Step 15.

NO : 

Repair or replace.

AK402097

1

2

3

AC

Connector: A-110

Harness side 
connector

A-110(B)

3

2

1

4

AK402084

J/B side 
connector

B-106

Connector: B-106
J/B (front side)

AC

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TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-158

STEP 15. Check harness between A-110 (terminal 
No. 3) camshaft position sensor connector and 
B-106 (terminal No. 4) engine control relay 
connector.

• Check power supply line for damage.

Q: Is the check result normal?

YES : 

Go to Step 16.

NO : 

Repair.

STEP 16. Connector check: A-114 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 17.

NO : 

Repair or replace.

STEP 17. Check harness between A-110 (terminal 
No. 2) camshaft position sensor connector and 
A-114 (terminal No. 12) engine-ECU connector.

AK402097

1

2

3

AC

Connector: A-110

Harness side 
connector

A-110(B)

3

2

1

4

AK402084

J/B side 
connector

B-106

Connector: B-106
J/B (front side)

AC

AK402745

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4

2

5

3

1

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L

AF

A-114

Connector: 

A-114

Harness side connector

Engine-ECU

Battery

AK402097

1

2

3

AC

Connector: A-110

Harness side 
connector

A-110(B)

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TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-159

• Check output line for damage.

Q: Is the check result normal?

YES : 

Go to Step 18.

NO : 

Repair.

STEP 18. Check harness between A-110 (terminal 
No. 1) camshaft position sensor connector and 
A-114 (terminal No. 27) engine-ECU connector.

• Check earthing line for damage.

Q: Is the check result normal?

YES : 

Go to Step 19.

NO : 

Repair.

STEP 19. Check camshaft position sensing 
cylinder.

Q: Is the check result normal?

YES : 

Go to Step 20.

NO : 

Replace the camshaft position sensing 
cylinder.

STEP 20. M.U.T.-III diagnosis code

• Reconfirmation of diagnosis code.

Q: Is the diagnosis code output?

YES : 

Replace camshaft position sensor.

NO : 

Intermittent malfunction (Refer to GROUP 
00 

− How to Use 

Troubleshooting/Inspection Service Points 

− 

How to Cope with Intermittent Malfunctions 

P.00-13

).

AK402745

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L

AF

A-114

Connector: 

A-114

Harness side connector

Engine-ECU

Battery

AK402097

1

2

3

AC

Connector: A-110

Harness side 
connector

A-110(B)

AK402745

6

4

2

5

3

1

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L

AF

A-114

Connector: 

A-114

Harness side connector

Engine-ECU

Battery

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TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-160

Code No. P0421: Warm Up Catalyst Malfunction

FUNCTION

• The signal from the oxygen sensor (rear) differs 

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

• The engine-ECU compares the output of the front 

and rear oxygen sensor signals.

TROUBLE JUDGMENT

Check Conditions

• The accelerator pedal is depressed.

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

• Air flow sensor output is 6 g/s or higher.

• 3 seconds or more elapsed after the abovemen-

tioned conditions were satisfied.

• Within the range of air-fuel ratio feed back opera-

tion

• Short-term fuel trim is more than -25% and is less 

than 15%

• Vehicle speed is 1.5 km/h or higher.

• For 10 seconds per cycle, the engine-ECU moni-

tors 7 cycles of this condition during the drive 
cycle.

• The cumulative air flow sensor output is more 

than a prescribed value.

Judgement Criterion

• The oxygen sensor (rear) signal frequency 

divided by oxygen sensor (front) signal frequency 
is 0.8 or more.

PROBABLE CAUSE

• Catalytic converter deteriorated

• Failed oxygen sensor (front)

• Failed oxygen sensor (rear)

• Failed engine-ECU

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. M.U.T.-II/III data list

• Refer to data list reference table 

P.13B-335

.

a. Item 11: Oxygen sensor (front)
b. Item 59: Oxygen sensor (rear)

Q: Is the check result 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 codes 

P.13B-18

).

STEP 3. M.U.T.-II/III data list

• Refer to data list reference table 

P.13B-335

.

a. Item 11: 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 oxygen sensor (front).

STEP 4. Replace the oxygen sensor (rear).

• After replacing the oxygen sensor (rear), 

re-check the trouble symptoms.

Q: Is the check result normal?

YES : 

Go to Step 5 .

NO : 

Check end.

STEP 5. Replace the catalytic converter.

• After replacing the catalytic converter, re-check 

the trouble symptoms.

Q: Is the check result normal?

YES : 

Replacing engine-ECU.

NO : 

Check end.

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