Mitsubishi Galant 9G. Manual — part 1031
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>
13B-424
STEP 14. Check the fuel pressure.
Refer to On-vehicle Service
− Fuel Pressure Test
Q: Is the fuel pressure normal?
YES : Go to Step 15.
NO : Repair it. Then go to Step 17.
STEP 15. Check for entry of foreign matter (water,
kerosene, etc.) into fuel.
Q: Are there any abnormalities?
YES : Go to Step 16.
NO : Replace the fuel. Then go to Step 17.
STEP 16. 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 −
(3) Check the diagnostic trouble code (DTC).
Q: Is DTC P0171 set?
YES : Replace the PCM. Then go to Step 17.
NO : The inspection is complete.
STEP 17. 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 −
(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0171 set?
YES : Retry the troubleshooting.
NO : The inspection is complete.
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-425
DTC P0172: System too Rich (bank 1)
CAUTION
If DTC P0172 has been set, TCL related DTC
U1120 is also set. After P0172 has been diag-
nosed, don't forget to erase DTC U1120.
.
Fuel Trim Circuit
• Refer to DTC P0201− Injector Circuit − Cylinder
1.
, P0203
− Injector Circuit − Cylinder
3.
, P0205
− Injector Circuit − Cylinder
5.
.
CIRCUIT OPERATION
• Refer to DTC P0201− Injector Circuit − Cylinder
1.
, P0203
− Injector Circuit − Cylinder
3.
, P0205
− Injector Circuit − Cylinder
5.
.
TECHNICAL DESCRIPTION
• If a malfunction occurs in the fuel system, the fuel
trim value becomes too small.
• 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 rich.
.
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
.
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>
13B-426
DTC SET CONDITIONS
Logic Flow Chart
.
Check Conditions
• 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 lower
than
−12.5 percent for 5 seconds.
or
• Short-term fuel trim has continued to be lower
than
−7.4 percent for 5 seconds.
Check Conditions
• 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.
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-427
Judgment Criteria
• Long-term fuel trim has continued to be lower
than
−12.5 percent for 5 seconds.
or
• Short-term fuel trim has continued to be lower
than
−12.5 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 −30.0
percent for 2 seconds.
.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function
− OBD-II Drive Cycle −
Procedure 2
− Fuel Trim Monitor
.
TROUBLESHOOTING HINTS (The most likely
causes for this code to be set are:)
• Mass airflow sensor failed.
• Injector (Number 1, 3, 5) failed.
• Incorrect fuel pressure.
• Engine coolant temperature sensor failed.
• Intake air temperature sensor failed.
• Barometric pressure sensor failed.
• Manifold absolute pressure sensor failed.
• 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
• MB991910: Main Harness A
STEP 1. 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 : YES: Go to Step 2.
NO : Refer to DTC P0101
− Mass Airflow Circuit
Range/Performance Problem
, DTC P0102
− Mass Airflow Circuit Low Input
, DTC
P0103
− Mass Airflow Circuit High Input
AC305412
AB
MB991910
DATA LINK
CONNECTOR
MB991824
MB991827
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