Mitsubishi Galant 9G. Manual - part 1033

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-432

STEP 10. Replace the right bank injector.
(1) Replace the right bank injector.
(2) Carry out a test drive with the drive cycle pattern. Refer to 

Diagnostic Function 

− OBD-II Drive Cycle − Procedure 2 − 

Fuel Trim Monitor 

P.13B-6

.

(3) Check the diagnostic trouble code (DTC).
Q: Is DTC P0172 set?

YES : Replace the PCM. Then go to Step 11.
NO :  The inspection is complete.

STEP 11. 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 2 − 

Fuel Trim Monitor 

P.13B-6

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0172 set?

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

DTC P0174: System too Lean (bank 2)

CAUTION

If DTC P0174 has been set, TCL related DTC 
U1120 is also set. After P0174 has been diag-
nosed, don't forget to erase DTC U1120.

.

Fuel Trim Circuit

• Refer to DTC P0202− Injector Circuit − Cylinder 

2.

P.13B-493

, P0204

− Injector Circuit − Cylinder 

4.

P.13B-516

, P0206

− Injector Circuit − Cylinder 

6.

P.13B-539

.

CIRCUIT OPERATION

• Refer to DTC P0202− Injector Circuit − Cylinder 

2.

P.13B-493

, P0204

− Injector Circuit − Cylinder 

4.

P.13B-516

, P0206

− Injector Circuit − Cylinder 

6.

P.13B-539

 

.

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

Left 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)

• Mass airflow sensor

• Engine coolant temperature sensor

• Intake air temperature sensor

• Barometric pressure sensor

• Throttle position sensor

.

AK303055

M

1

2

CONNECTOR: B-01, B-03, B-04

AB

B-01 (GR)

B-03 (GR)

B-04 (GR)

HARNESS CONNECTOR:
COMPONENT SIDE

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-433

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 76°C 

(169

°F).

• Mass airflow sensor output is 8 g/sec or more.

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.

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

AK204050

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-434

Check Conditions

• Engine coolant temperature is lower than 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 76°C 

(169

°F).

• Mass airflow sensor output is 8 g/sec or less.

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 higher than 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 76°C 

(169

°F).

• Mass airflow sensor output is 8 g/sec or more.

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 +17.6 percent for 5 seconds.

Check Conditions

• Engine coolant temperature is higher than 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 76°C 

(169

°F).

• Mass airflow sensor output is 8 g/sec or less.

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 +17.6 percent for 5 seconds.

Check Conditions

• Engine coolant temperature is higher than 76°C 

(169

°F).

• Under the closed loop air/fuel ratio control.

Judgment Criteria

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

percent for 2 seconds.

or

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

percent for 2 seconds.

.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 2 

− Fuel Trim Monitor 

P.13B-6

.

.

TROUBLESHOOTING HINTS (The most likely 

causes for this code to be set are:)

• Mass airflow sensor failed.

• Injector (Number 2, 4, 6) 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.

• Manifold absolute pressure sensor failed.

• Exhaust leak.

• Use of incorrect or contaminated fuel.

• Harness damage in left bank injector circuit or 

connector damage.

• PCM failed.

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-435

DIAGNOSIS

Required Special Tools:

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

• MB991824: V.C.I.

• MB991827: USB Cable

• MB991910: Main Harness A

STEP 1. Check for exhaust leak.
Q: Are there any abnormalities?

YES : Repair it. Then go to Step 15.
NO :  Go to Step 2.

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

YES : Repair it. Then go to Step 15.
NO :  Go to Step 3.

STEP 3. Using scan tool MB991958, check data list item 12: 
Mass 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, Mass Airflow Sensor.

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

°C 

to 95

°C (176°F to 203°F).

• When idling, between 2.0 and 6.0 g/sec.

• When 2,500 r/min, between 8.0 and 16.0 g/sec.

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

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

− Mass Airflow Circuit 

Range/Performance Problem 

P.13B-46

, DTC P0102 

− Mass Airflow Circuit Low Input 

P.13B-57

, DTC 

P0103 

− Mass Airflow Circuit High Input 

P.13B-67

.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827