Mitsubishi Colt Ralliart. Manual - part 51

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4A9>

13A-158

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 <M/T> or engine-CVT-ECU 

<CVT> compares the output of the oxygen sen-
sor signals (front and rear).

TROUBLE JUDGMENT

Check Conditions

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

• The accelerator pedal is open.

• 3 seconds or more elapsed after the above men-

tioned conditions were satisfied.

• 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-CVT-ECU <CVT> monitors 7 
cycles of this condition during the drive cycle.

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

and +25 % or lower.

Judgment Criterion

• The oxygen sensor (rear) signal frequency 

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

PROBABLE CAUSES

• Catalytic converter deteriorated

• Failed oxygen sensor (front)

• Failed oxygen sensor (rear)

• Failed engine-ECU <M/T> or engine-CVT-ECU 

<CVT>

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.-III data list

• Refer to Data List Reference Table 

P.13A-331

.

a. Item 11: Oxygen sensor (front)
b. Item 59: 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. M.U.T.-III data list

• 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 : 

Check end.

NO : 

Go to Step 5 .

STEP 5. Replace the catalytic converter.

• After replacing the catalytic converter, re-check 

the trouble symptoms.

Q: Is the check result normal?

YES : 

 Replace engine-ECU <M/T> or 

engine-CVT-ECU <CVT>.

NO : 

Check end.

Main

Index

Group

TOC

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4A9>

13A-159

Code No. P0443: Purge Control Solenoid Valve System

OPERATION

• Power is supplied to the purge control solenoid 

valve (terminal No. 2) from the engine control 
relay (terminal No. 4).

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

<CVT> (terminal No. 38) makes the power tran-
sistor in the unit be in ON position, and that 
makes currents go on the purge control solenoid 
valve (terminal No. 1).

AK402707

3

1

2

4

1 2

19

21

20

18

17

16

15

14

1213

11

8 9

L

10

37
52 53 54 555657585960616263646566

38 39 404142434445464748495051

22 23 24 252627282930313233343536

7

5

3

1

6

4

2

Engine
control
relay

B-106

4

2

38

Engine-ECU <M/T> or
engine-CVT-ECU <CVT>

To engine-ECU <M/T> or
engine-CVT-ECU <CVT>

    A-108
MU802779

B-112

A-17

B-108

Purge control
solenoid valve

1

2

4

6

Purge Control Solenoid Valve Circuit

R

R

L-R

3

1

A-114

1

1

R

Fusible link

16

20A

J/B

AC

Wire colour code
B: Black  LG: Light green  G: Green  L: Blue  W: White  Y: Yellow  SB: Sky blue  BR: Brown  O: Orange  GR: Gray
R: Red  P: Pink  V: Violet  Pu: Purple

Main

Index

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TOC

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4A9>

13A-160

FUNCTION

• In response to a signal from the engine-ECU 

<M/T> or engine-CVT-ECU <CVT>, the purge 
control solenoid valve controls the flow rate of the 
purge air to be introduced into the surge tank.

TROUBLE JUDGMENT

Check Conditions

• Engine is running <M/T>.

• Battery positive voltage is more than 10 V and is 

less than 16 V <M/T>.

• Engine speed is more than 1,200 r/min and is 

less than 3,000 r/min <M/T>.

• Ignition switch is in ON position <CVT>.

• Battery positive voltage is 10 V or higher <CVT>.

Judgment Criterion

• The surge voltage (system voltage +2 V) of sole-

noid coil is not detected when the purge control 
solenoid valve is turned in OFF position from ON.

PROBABLE CAUSES

• Failed purge control solenoid valve

• Open/short circuit in purge control solenoid value 

circuit or loose connector contact

• Failed engine-ECU <M/T> or engine-CVT-ECU 

<CVT>

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III actuator test

• Item 08: Purge control solenoid valve

OK: Operating sound can be heard and the 
valve vibrates

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use 

Troubleshooting/Inspection Service Points 

− 

How to Cope with Intermittent Malfunctions 

P.00-13

).

NO : 

Go to Step 2 .

STEP 2. Connector check: A-108 purge control 
solenoid valve connector

Q: Is the check result normal?

YES : 

Go to Step 3 .

NO : 

Repair or replace the connector.

STEP 3. Perform resistance measurement at 
A-108 purge control solenoid valve connector.

• Disconnect connector, and measure at solenoid 

valve side.

• Resistance between terminal No. 1 and No. 2.

OK: 30 

− 34 Ω (at 20°C)

Q: Is the check result normal?

YES : 

Go to Step 4 .

NO : 

Replace purge control solenoid valve.

AK402007

1

2

AC

Connector: A-108

A-108 (B)

A-108 Harness side
connector

AK402007

1

2

AC

Connector: A-108

A-108 (B)

A-108 Harness side
connector

Main

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TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4A9>

13A-161

STEP 4. Perform voltage measurement at A-108 
purge control solenoid valve connector.

• Disconnect connector, and measure at harness 

side.

• Ignition switch: ON

• Voltage between terminal No. 2 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 6 .

NO : 

Go to Step 5 .

STEP 5. Connector check: B-106 engine control 
relay connector

Q: Is the check result normal?

YES : 

Check intermediate connector A-17 and 

B-112, and repair if necessary. If 
intermediate connector is normal, check and 
repair harness between A-108 (terminal No. 
2) purge control solenoid valve connector 
and B-106 (terminal No. 4) engine control 
relay connector.

• Check power line for open/short 

circuit.

NO : 

Repair or replace the connector.

AK402007

1

2

AC

Connector: A-108

A-108 (B)

A-108 Harness side
connector

3

2

1

4

AK402060

B-106
J/B side 
connector

B-106

Connector: B-106
J/B (front side)

AC

AK402007

1

2

AC

Connector: A-108

A-108 (B)

A-108 Harness side
connector

Main

Index

Group

TOC