Mitsubishi Galant 9G. Manual — part 741
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-406
13A
DTC P0171: System too Lean (cylinder 1, 4)
CAUTION
If DTC P0171 has been set, TCL related DTC
U1120 is also set. After P0171 has been diag-
nosed, don't forget to erase DTC U1120.
.
Fuel Trim Circuit
• Refer to DTC P0201 − Injector Circuit-cylinder 1
, DTC P0204
− Injector Circuit-cylinder
4
.
CIRCUIT OPERATION
• Refer to DTC P0201 − Injector Circuit-cylinder 1
, DTC P0204
− Injector Circuit-cylinder
4
.
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
Cylinder 1, 4 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
.
<<PREVIOUS
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-407
DTC SET CONDITIONS
Logic Flow Chart
.
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 6 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 +10.0 percent for 5 seconds. <Federal>
or
• Short-term fuel trim has continued to be higher
than +7.0 percent for 5 seconds. <California>
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) <2.4L ENGINE>
13A-408
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 6 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 +15.0 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 6 g/sec or more.
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 +20.0 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 6 g/sec or less.
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 +25.0 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
.
TROUBLESHOOTING HINTS (The most likely
causes for this code to be set are:)
• Mass airflow sensor failed.
• Injector (Number 1, 4) 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 cylinder 1, 4 injector circuit or
connector damage.
• PCM failed.
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-409
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 6.5 and 14.5 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
, DTC P0102
− Mass Airflow Circuit Low Input
, DTC
P0103
− Mass Airflow Circuit High Input
AK303804AB
MB991910
DATA LINK
CONNECTOR
MB991824
MB991827
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