Mitsubishi Montero Sport (2004+). Manual - part 283

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-545

Judgment Criteria

• If the voltage signal from the fuel tank differential 

pressure sensor changes by 0.2 volt or more, 
DTC P0451 will set. The code may also set if a 
sudden pressure fluctuation occurs twenty times 
while the engine is idling, and then eight consec-
utive times during normal driving.
NOTE: If the number of the sudden pressure fluc-
tuation does not reach twenty during one engine 
idling, the counter will be reset to zero. If the igni-
tion switch is turned off, it will be also reset to 
zero.
NOTE: The conditions for deviating from idling 
operation are as follows:

.

•

Engine speed is higher than 2,500 r/min.

•

Vehicle speed is 15 km/h (9.3 mph) or more.

•

Volumetric efficiency is 55 percent or more.

.

OBD-ll DRIVE CYCLE PATTERN
Refer to Diagnostic Function 

− OBD-ll Drive Cycle − 

Procedure 1 

− Evaporative Emission System Leak 

Monitor 

P.13A-4

.

.

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

• Malfunction of the fuel tank differential pressure 

sensor.

• A damaged harness in the fuel tank differential 

pressure sensor circuit.

• Malfunction of the PCM.

.

OVERVIEW OF TROUBLESHOOTING

•  DTC P0451 can be set by a faulty fuel tank differ-

ential pressure sensor or related circuit, or PCM 
failure.

• To check a system blockage, do a performance 

test which uses a mechanical vacuum gauge and 
scan tool MB991958 set on the fuel tank differen-
tial pressure sensor (TANK PRS SNSR 73).
The mechanical gauge reading is used to verify 
scan tool MB991958 reading.
A comparison of the mechanical gauge with the 
reading on scan tool MB991958 will locate a 
problem in the system.

DIAGNOSIS

Required Special Tools:

• MB991958: Scan tool (MUT-III sub assembly)

• MB991824: V.C.I.

• MB991827: MUT-III USB cable

• MB991911: MUT-III main harness B

• MB991658: Test harness set

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-546

STEP 1. Using scan tool MB991958, check data list item 73: 
Fuel Tank Differential Pressure Sensor.

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) Disconnect hose E from the evaporative emission canister 

side, and plug the hose.

(3) Turn the ignition switch to the "ON" position.
(4) Remove the fuel cap.
(5) Set scan tool MB991958 to the data reading mode.

• Item 73, Fuel Tank Differential Pressure Sensor.

• The fuel tank pressures reading on the scan tool 

should be 

−3.3 to 3.3 kPa (−0.97 to 0.97 inHg).

(6) Connect an evaporative emission system pressure pump to 

the fuel filler neck and pressurize the fuel tank.

• The fuel tank pressure reading should increase.

(7) Turn the ignition switch to the "LOCK" (OFF) position. Then 

disconnect scan tool MB991958.

(8) Disconnect the evaporative emission system pressure 

pump, and reinstall the fuel cap.

(9) Connect hose E to the canister.
Q: Is the fuel tank pressure between 

−3.3 and 3.3 kPa 

(

−0.97 and 0.97 inHg)?

YES : It can be assumed that this malfunction is intermittent. 

(Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

− How to 

Cope with Intermittent Malfunction 

P.00-7

). Then go 

to Step 16 .

NO :  Go to Step 2 .

AK303629AB

MB991911

MB991827

MB991824 

16-PIN

AC005140

HOSE E

AC

ACX01358

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-547

STEP 2. Measure the sensor output voltage at fuel tank 
differential pressure sensor connector E- 28.
(1) Disconnect hose E from the evaporative emission canister 

side, and plug the hose.

(2) Remove the fuel tank mounting nuts, tilt the fuel tank.

(3) Disconnect fuel tank differential pressure sensor connector 

E-28.

(4) Connect special tool MB991658 between pressure sensor 

connector terminal 1, 2 and 3.

(5) Turn the ignition switch to the "ON" position.
(6) Remove the fuel cap.
(7) Measure the voltage between terminal 1 and ground.

• The measured voltage should measure between 2.0 

and 3.0 volts.

(8) Turn the ignition switch to the "LOCK" (OFF) position.
(9) Disconnect the evaporative emission system pressure 

pump, and reinstall the fuel cap.

(10)Connect hose E to the canister.
Q: Is the measured voltage between 2.0 and 3.0 volts?

YES : Go to Step 7 .
NO :  Go to Step 3 .

AC005140

HOSE E

AC

AC002614

CONNECTOR: E-28

FUEL TANK
DIFFERENTIAL
PRESSURE
SENSOR

AH

E-28 (B)

2 1

3

E-28 HARNESS SIDE 
CONNECTOR

AC002081AB

MB991658

FUEL TANK DIFFERENTIAL 
PRESSURE SENSOR

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-548

STEP 3. Measure the 5-volt supply circuit voltage at fuel 
tank differential pressure sensor connector E-28.
(1) Disconnect fuel tank differential pressure sensor connector 

E-28.

(2) Connect special tool MB991658 between pressure sensor 

connector terminal 1, 2 and 3.

(3) Turn the ignition switch to the "ON" position.
(4) Measure the voltage between terminal 3 and ground.

• Voltage should measure between 4.7 and 5.1 volts.

(5) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 4.7 and 5.1 volts?

YES : Go to Step 4 .
NO :  Go to Step 10 .

STEP 4. Check the ground circuit voltage at fuel tank 
differential pressure sensor connector E-28. 
(1) Disconnect fuel tank differential pressure sensor connector 

E-28.

(2) Use special tool MB991658 to connect terminal 3 of the 

disconnected sensor connector and those of the harness 
side connector respectively.

(3) Turn the ignition switch to the "ON" position.
(4) Measure the voltage at the fuel tank differential pressure 

sensor side connector between terminal 2 and ground.

• Voltage should measure 0.5 volt or less.

(5) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage 0.5 volt or less?

YES : Go to Step 5 .
NO :  Go to Step 12 .

AC002614

CONNECTOR: E-28

FUEL TANK
DIFFERENTIAL
PRESSURE
SENSOR

AH

E-28 (B)

2 1

3

E-28 HARNESS SIDE 
CONNECTOR

AC002081AB

MB991658

FUEL TANK DIFFERENTIAL 
PRESSURE SENSOR

AC002614

CONNECTOR: E-28

FUEL TANK
DIFFERENTIAL
PRESSURE
SENSOR

AH

E-28 (B)

2 1

3

E-28 HARNESS SIDE 
CONNECTOR

AC002081AB

MB991658

FUEL TANK DIFFERENTIAL 
PRESSURE SENSOR