Mitsubishi Montero (2004+). Manual - part 204

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-303

DTC SET CONDITIONS

Logic Flow Chart

.

Check Conditions

• 20 seconds or more have passed since the 

engine starting sequence was completed.

• Engine coolant temperature is higher than 76°C 

(169

° F).

• Engine speed is higher than 1,200 r/min.

• Volumetric efficiency is between 30 and 80 per-

cent.

• Throttle position sensor output voltage is lower 

than 4 volts.

• Except while fuel is being shut off.

• Monitoring time: 30 seconds.

Judgment Criteria

• Left bank heated oxygen sensor (front) output 

voltage does not get across 0.5 volt within about 
30 seconds.

.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 6 

− Other Monitor 

P.13A-4

.

.

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

• Left bank heated oxygen sensor (front) deterio-

rated.

• Harness damage in left bank heated oxygen sen-

sor (front) output line.

• Left bank heated oxygen sensor (rear) deterio-

rated.
NOTE: When the left bank heated oxygen sensor 
(front) begins to deteriorate, the heated oxygen 
sensor output voltage will deviate from the volt-
age when the sensor was new (normally 0.5 volt 
at stoichiometric ratio). This deviation will be cor-
rected by the left bank heated oxygen sensor 
(rear).

HEATED OXYGEN SENSOR (FRONT) 

OUTPUT VOLTAGE CROSSES 0.5V?

START

END

NO

NO

NO

YES

Yes

YES

MALFUNCTION

GOOD

30secs HAVE PASSED?

MONITORING

CONDITIONS

AK302933

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-304

If the left bank heated oxygen sensor (rear) 
responds poorly because it has deteriorated, it 
will improperly correct the left bank heated oxy-
gen sensor (front). Thus, even when closed loop 
control is being effected, the fluctuation of the left 
bank heated oxygen sensor (front) output voltage 
decreases, without intersecting with 0.5 volt. As a 
result, there is a possibility of DTC P0154 becom-
ing registered.

• Open circuit in left bank injector.

• Harness damage in left bank injector circuit.

• Connector damage.

• PCM failed.

• Exhaust leak.

• Air drawn in from gaps in gasket, seals, etc.

• Incorrect fuel pressure.

DIAGNOSIS

Required Special Tools:

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991911: Main Harness B

• MD991316: Test Harness

STEP 1. Using scan tool MB991958, check data list item 59: 
Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Start the engine and run at idle.

(3) Set scan tool MB991958 to the data reading mode for item 

59, Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).

• Warming up the engine. When the engine is revved, the 

output voltage should repeat 0 volt and 0.6 to 1.0 volt 
alternately.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?

YES : Go to Step 2. 
NO :  Refer to DTC P0156 

− Heated Oxygen Sensor Circuit 

(bank 2, sensor 2) 

P.13A-322

, DTC P0157 

− Heated 

Oxygen Sensor Circuit Low Voltage (bank 2, sensor 
2) 

P.13A-338

, DTC P0158-Heated Oxygen Sensor 

Circuit High Voltage (bank 2, sensor 2) 

P.13A-345

, 

DTC P0159 

− Heated Oxygen Sensor Circuit Slow 

Response (bank 2, sensor 2) 

P.13A-350

. 

STEP 2. Check the exhaust leak.
Q: Are there any abnormalities?

YES : Repair it. Then go to Step 12.
NO :  Go to Step 3.

STEP 3. Check the intake system vacuum leak.
Q: Are there any abnormalities?

YES : Repair it. Then go to Step 12.
NO :  Go to Step 4.

AK302970

AB

MB991911

MB991824

MB991827

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-305

STEP 4. Check connector B-26 at the left bank heated 
oxygen sensor (front) for damage.

Q: Is the connector in good condition?

YES : Go to Step 5.
NO :  Repair or replace it. Refer to GROUP 00E, Harness 

Connector Inspection 

P.00E-2

. Then go to Step 14.

AK201278

1

2

3

4

CONNECTOR: B-26

B-26(GR)

AC

HARNESS 
CONNECTOR: 
COMPONENT 
SIDE

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-306

STEP 5. Check the left bank heated oxygen sensor (front).

(1) Disconnect the left bank heated oxygen sensor (front) 

connector B-26 and connect test harness special tool 
MB991316 to the connector on the left bank heated oxygen 
sensor (front) side.

(2) Warm up the engine until engine coolant temperature 

reaches 80

°C (176°F) or higher.

(3) Perform a racing for 5 minutes or more with the engine 

speed of 4,500 r/min.

(4) Connect a digital voltage meter between terminal No. 2 

(black clip of special tool) and terminal No. 4 (white clip of 
special tool).

(5) While repeatedly revving the engine, measure the left bank 

heated oxygen sensor (front) output voltage.

Standard value: 0.6 

− 1.0 volt

CAUTION

• Be very careful when connecting the jumper wires; 

incorrect connection can damage the left bank heated 
oxygen sensor (front).

• Be careful the heater is broken when voltage of beyond 

8 volts is applied to the left bank heated oxygen sensor 
(front) heater.
NOTE: If the sufficiently high temperature [of approximate 
400

°

C (752

°

F) or more] is not reached although the left 

bank heated oxygen sensor (front) is normal, the output 
voltage would be possibly low although the rich air/fuel 
ratio. Therefore, if the output voltage is low, use a jumper 
wire to connect the terminal No. 1 (red clip of special tool) 
and the terminal No. 3 (blue clip of special tool) of the left 
bank heated oxygen sensor (front) with the positive terminal 
and the negative terminal of 8 volts power supply respec-
tively, then check again.

Q: Is the voltage between 0.6 and 1.0 volt?

YES : Go to Step 6.
NO :  Replace the left bank heated oxygen sensor (front). 

Then go to Step 14.

STEP 6. Check connector B-44 at injector intermediate 
connector for damage.

Q: Is the connector in good condition?

YES : Go to Step 7.
NO :  Repair or replace it. Refer to GROUP 00E, Harness 

Connector Inspection 

P.00E-2

. Then go to Step 14.

AK201278

1

2

3

4

CONNECTOR: B-26

B-26(GR)

AC

HARNESS 
CONNECTOR: 
COMPONENT 
SIDE

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

AKX01624

HEATED
OXYGEN
SENSOR
COMPONENT
SIDE
CONNECTOR

MB991316

WHITE

BLACK

AN

AK200949

3

4

7

8

1

2

5

6

B-44(B)

CONNECTOR: B-44

AB

HARNESS 
CONNECTOR: 
COMPONENT SIDE