Mitsubishi Montero (2004+). Manual — part 199

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-283

STEP 14. 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 wire;

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 : Replace the PCM. Then go to Step 15.
NO : Replace the left bank heated oxygen sensor (front).

Then go to Step 15.

STEP 15. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to

Diagnostic Function

− OBD-II Drive Cycle − Procedure 6 −

Other Monitor

P.13A-4

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0150 set?

YES : Retry the troubleshooting.
NO : The inspection is complete.

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

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-284

DTC P0151: Heated Oxygen Sensor Circuit Low Voltage (bank 2, sensor 1)

BL

ACK

BL

ACK

BL

ACK

TO PCM

FROM MFI RELAY

WHITE

AK201135

96

108

4

3

1

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

POWERTRAIN CONTROL
MODULE (PCM)

11

9

7

2

4

3

1 2

B-26

MU802665

1

12

23 24 25 26

2

13

3

14

4

15

5

16

6

17

7

18

8

19

9

20 21 22

27 28 29 30 31 32 33

10 11

D-116

1
5

7 8

3 4
9 10

2
6

D-14

MU801335

Left Bank Heated Oxygen Sensor (front) Circuit

9192

939495

96979899

100

105

113114

115116117

118119120

106

107108109

110111112

101102103

104

D-135

(MU803805)

AK201277

CONNECTOR: B-26

B-26(GR)

AD

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

AK201038AF

CONNECTOR: D-135

PCM

D-135(GR)

AK201049

D-14

AB

CONNECTOR: D-14

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-285

.

CIRCUIT OPERATION

• A voltage corresponding to the oxygen concen-

tration in the exhaust gas is sent to the PCM (ter-
minal No. 108) from the output terminal (terminal
No. 4) of the left bank heated oxygen sensor
(front).

• Terminal No. 2 of the left bank heated oxygen

sensor (front) is grounded with PCM (terminal
No. 96).

.

TECHNICAL DESCRIPTION

• The left bank heated oxygen sensor (front)

detects the concentration of oxygen in the
exhaust gas; it converts that data to voltage, and
sends it to the PCM.

• When the left bank heated oxygen sensor (front)

begins to deteriorate, the heated oxygen sensor
signal response deteriorates also.

• The PCM varies the air/fuel mixture to make it

leaner and richer, and checks the response
speed of the left bank heated oxygen sensor
(front). In addition, the PCM also checks for an
open circuit in the left bank heated oxygen sensor
(front) output line.

.

DESCRIPTIONS OF MONITOR METHODS
Left bank heated oxygen sensor (front) output volt-

age stays low when air/fuel ratio is forced to be
rich. The above procedure is repeated when oxy-
gen sensor is inactive.

.

MONITOR EXECUTION
Continuous

.

MONITOR EXECUTION CONDITIONS (Other
monitor and Sensor)

Other Monitor (There is no temporary DTC stored

in memory for the item monitored below)

• Heated oxygen sensor heater (front) monitor

• Misfire monitor

• Fuel system monitor

Sensor (The sensor below is determined to be

normal)

• Volume airflow sensor

• Engine coolant temperature sensor

• Intake air temperature sensor

• Barometric pressure sensor

• Throttle position sensor

• Accelerator pedal position sensor

.

AK201049

CONNECTOR: D-116

D-116

AC

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-286

DTC SET CONDITIONS

Logic Flow Chart

.

Check Conditions

• 3 minutes or more have passed since the engine

starting sequence was completed.

• Left bank heated oxygen sensor (front) signal

voltage has continued to be 0.2 volt or lower.

• Engine coolant temperature is higher than 76°C

(169

°F).

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

• Volumetric efficiency is higher than 25 percent.

• Volume airflow sensor output frequency is higher

than 100 Hz.

• At least 20 seconds have passed since fuel shut

off control was canceled.

START

V

F

> =4.5V

2secs HAS PASSED

YES

YES

YES

NO

NO

NO

MALFUNCTION

MONITORING

CONDITIONS

YES

NO

MONITORING

CONDITIONS

+5V ON

AK302930

V

F

< 0.2V

10secs HAS PASSED

YES

YES

NO

NO

END

MALFUNCTION

GOOD

MODULATE A/F CONDITION TO RICH