Mitsubishi Montero (2004+). Manual - part 220

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-367

STEP 11. Check the trouble symptoms.

(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 P0161 set?

YES : Replace the PCM. Then go to Step 12.
NO :  It can be assumed that this malfunction is intermittent. 

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

P.00-6

. 

STEP 12. 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 P0161 set?

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

DTC P0171: System too Lean (bank 1)

.

Fuel Trim Circuit

• Refer to DTC P0201 − P0206, Injector Circuit. 

P.13A-421

.

CIRCUIT OPERATION

• Refer to DTC P0201 − P0206, Injector Circuit. 

P.13A-421

.

TECHNICAL DESCRIPTION

• If a malfunction occurs in the fuel system, the fuel 

trim value becomes too large.

• The PCM checks whether the fuel trim value is 

within a specified range.

.

DESCRIPTIONS OF MONITOR METHODS
Right bank air/fuel learning value (long time fuel trim) 

and air/fuel feedback integral value (short time 
fuel trim) are too lean.

.

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)

• Misfire 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

.

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-368

DTC SET CONDITIONS

Logic Flow Chart

Check Conditions

• Engine coolant temperature is lower than approx-

imately 100

°C (212°F) when the engine is 

started.

• Intake air temperature is lower than 60°C (140°F) 

when the engine is started.

• Under the closed loop air/fuel ratio control.

• Engine coolant temperature is higher than 77°C 

(171

°F).

• Volume airflow sensor output frequency is higher 

than 100 Hz.

Judgment Criteria

• Long-term fuel trim has continued to be higher 

than +12.5 percent for 5 seconds.

or

• Short-term fuel trim has continued to be higher 

than +7.4 percent for 5 seconds.

Check Conditions

• Engine coolant temperature is lower than approx-

imately 100

°C (212°F) when the engine is 

started.

• Intake air temperature is lower than 60°C (140°F) 

when the engine is started.

• Under the closed loop air/fuel ratio control.

K

LRN

: LONG-TERM TRIM

K

I

: SHORT-TERM TRIM

K0 : MAXIMUM LIMIT OF LONG-TERM TRIM
K1 : MAXIMUM LIMIT OF SHORT-TERM TRIM
K2 : MINIMUM LIMIT OF LONG-TERM TRIM
K3 : MINIMUM LIMIT OF SHORT-TERM TRIM

START

MONITORING

CONDITIONS

END

NO

NO

NO

NO

NO

NO

YES

YES

YES

YES

YES

YES

K

LRN

 > K0

MALFUNCTION

GOOD

K

LRN

 < K2

K

I

< K3

K

I

> K1

CONTINUOUS FAILURE

FOR 5secs

AK302938

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-369

• Engine coolant temperature is higher than 77°C 

(171

°F).

• Volume airflow sensor output frequency is higher 

than 100 Hz.

Judgment Criteria

• Long-term fuel trim has continued to be higher 

than +12.5 percent for 5 seconds.

or

• Short-term fuel trim has continued to be higher 

than +12.5 percent for 5 seconds.

Check Conditions

• Engine coolant temperature is higher than 

approximately 100

°C (212°F) when the engine is 

started.

• Intake air temperature is higher than 60°C 

(140

°F) when the engine is started.

• Under the closed loop air/fuel ratio control.

• Engine coolant temperature is higher than 77°C 

(171

°F).

• Volume airflow sensor output frequency is higher 

than 100 Hz.

Judgment Criteria

• Long-term fuel trim has continued to be higher 

than +12.5 percent or 5 seconds.

or

• Short-term fuel trim has continued to be higher 

than +17.6 percent for 5 seconds.

Check Conditions

• Engine coolant temperature is higher than 

approximately 100

°C (212°F) when the engine is 

started.

• Intake air temperature is higher than 60°C 

(140

°F) when the engine is started.

• Under the closed loop air/fuel ratio control.

• Engine coolant temperature is higher than 77°C 

(171

°F).

• Volume airflow sensor output frequency is lower 

than 100 Hz.

Judgment Criteria

• Long-term fuel trim has continued to be higher 

than +12.5 percent or 5 seconds.

or

• Short-term fuel trim has continued to be higher 

than +22.3 percent for 5 seconds.

Check Conditions

• Engine coolant temperature is higher than 77°C 

(171

°F).

• Under the closed loop air/fuel ratio control.

Judgment Criteria

• Long-term fuel trim has continued to be +12.5 

percent for 5 seconds.

or

• Short-term fuel trim has continued to be +25.0 

percent for 5 seconds.

.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 2 

− Fuel Trim Monitor 

P.13A-4

.

.

TROUBLESHOOTING HINTS (The most likely 

causes for this code to be set are: )

• Volume airflow sensor failed.

• Injector (Number 1, 3, 5) failed.

• Incorrect fuel pressure.

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

• Engine coolant temperature sensor failed.

• Intake air temperature sensor failed.

• Barometric pressure sensor failed.

• Exhaust leak.

• Use of incorrect or contaminated fuel.

• Harness damage in right bank injector circuit or 

connector damage.

• PCM failed.

DIAGNOSIS

Required Special Tools:

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

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991911: Main Harness B

STEP 1. Check the exhaust leaks.
Q: Are there any abnormalities?

YES : Go to Step 2.
NO :  Repair it. Then go to Step 16.

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-370

STEP 2. Check the intake system vacuum leak.
Q: Are there any abnormalities?

YES : Go to Step 3.
NO :  Repair it. Then go to Step 16.

STEP 3. Using scan tool MB991958, check data list item 12: 
Volume Airflow 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) Start the engine and run at idle.

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

12, Volume Airflow Sensor.

(4) Warm up the engine to normal operating temperature: 80

°C 

to 95

°C (176°F to 203°F).

• When idling, between 17 and 43 Hz (between 3.5 and 

7.5 gm/s).

• When 2,500 r/min, between 64 and 104 Hz (between 

13.6 and 19.6 gm/s).

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

YES : YES: Go to Step 4.
NO :  Refer to DTC P0101 

− Volume Airflow Circuit 

Range/Performance Problem 

P.13A-33

, DTC P0102 

− Volume Airflow Circuit Low Input 

P.13A-42

.

STEP 4. Using scan tool MB991958, check data list item 13: 
Intake Air Temperature Sensor.

(1) Turn the ignition switch to the "ON" position.
(2) Set scan tool MB991958 to the data reading mode for item 

13, Intake Air Temperature Sensor.

• The intake air temperature and temperature shown with 

the scan tool should approximately match.

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

YES : Go to Step 5.
NO :  Refer to DTC P0111 

− Intake Air Temperature Circuit 

Range/Performance Problem 

P.13A-95

, DTC P0112 

− Intake Air Temperature Circuit Low Input 

P.13A-102

, DTC P0113 

− Intake Air Temperature 

Circuit High Input 

P.13A-107

.

AK302970

AB

MB991911

MB991824

MB991827

AK302970

AB

MB991911

MB991824

MB991827