Mitsubishi Montero (2002-2004). Manual - part 685

TSB Revision

DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-437

AC203992

Fuel Tank Differential Pressure Sensor Circuit

AB

TSB Revision

DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-438

.

CIRCUIT OPERATION

• The PCM (terminal 97) supplies a 5-volt refer-

ence signal to the fuel tank differential pressure 
sensor (terminal 3). The fuel tank differential 
pressure sensor (terminal 2) is grounded through 
the PCM (terminal 96).

• The fuel tank differential pressure sensor (termi-

nal 1) returns a voltage signal to the PCM (termi-
nal 82) that is proportional to the pressure in the 
fuel tank.

.

TECHNICAL DESCRIPTION

• The PCM monitors the fuel tank differential pres-

sure sensor output voltage.

• The PCM determines whether the fuel tank differ-

ential pressure sensor signal voltage is within 
normal operating parameters.

.

DTC SET CONDITIONS

Test Conditions:

• Throttle valve is closed.

• Vehicle speed is less than 1.5 km/h (0.93 mph).

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 sudden pressure fluctua-
tions does not reach twenty during any one 
period of engine idling, or the ignition switch is 
turned "LOCK" (OFF) position, the counter will 
reset to zero.
NOTE:  The conditions for deviating from idling 
operation are as follows:

.

AC203998

CONNECTOR: D-112

AB

D-112

AC203993

CONNECTORS: D-134, D-135

AB

D-134
(GR)

D-135
(GR)

PCM

AC203999

CONNECTORS: E-111, E-113

AB

E-113

E-111

AC204000

CONNECTOR: F-07

AB

F-07 (B)

ACX00218

CONNECTOR : G-05

AQ

G-05 (B)

SECOND SEAT UNDER
SERVICE HOLE

TSB Revision

DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-439

•

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

•

Vehicle speed is greater than 15 km/h (9.3 
mph).

•

Volumetric efficiency is greater than 55 per-
cent.

.

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 MB991502 set on the fuel tank differen-
tial pressure sensor (TANK PRS SNSR 73).
The mechanical gauge reading is used to verify 
scan tool MB991502 reading.
A comparison of the mechanical gauge with the 
reading on scan tool MB991502 will locate a 
problem in the system.

TSB Revision

DIAGNOSTIC TROUBLE CODE PROCEDURES

13Ac-440

DIAGNOSIS

Required Special Tools:

• MB991502: Scan Tool (MUT-II)

• MB991658: Test Harness Set

STEP 1. Using scan tool MB991502, check data list item 73: 
Fuel Tank Differential Pressure Sensor.

CAUTION

To prevent damage to scan tool MB991502, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991502.
(1) Connect scan tool MB991502 to the data link connector.

(2) Disconnect hose F 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 MB991502 to the data reading mode for 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 tank filler tube and pressurize the fuel tank.

• The fuel tank pressure reading should increase.

(7) Disconnect an evaporative emission system pressure pump 

and connect hose F.

(8) Turn the ignition switch to the "LOCK" (OFF) position and 

disconnect scan tool MB991502.

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.00-6

). Go to Step 15.

NO :  Go to Step 2.

ACX01539

16-PIN

MB991502

AC

AC102602 AC

HOSE F

ACX01358