Mitsubishi Galant 9G. Manual — part 1009
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>
13B-336
.
CIRCUIT OPERATION
• A voltage corresponding to the oxygen concen-
tration in the exhaust gas is sent to the PCM (ter-
minal No. 91) from the output terminal (terminal
No. 4) of the left bank heated oxygen sensor
(front).
• Terminal No. 2 of the left bank heated oxygen
sensor (front) is grounded with PCM (terminal
No. 69).
.
TECHNICAL DESCRIPTION
• The left bank heated oxygen sensor (front)
detects the concentration of oxygen in the
exhaust gas; it converts those data to voltage,
and inputs the resulting signals to the PCM.
• When the left bank heated oxygen sensor (front)
begins to deteriorate, the left bank heated oxygen
sensor signal response becomes poor.
• The PCM forcibly varies the air/fuel mixture to
make it leaner and richer, and checks the
response speed of the left bank heated oxygen
sensor (front). In addition, the PCM also checks
for an open circuit in the left bank heated oxygen
sensor (front) output line.
.
DESCRIPTIONS OF MONITOR METHODS
Left bank heated oxygen sensor (front) rich/lean
switching frequency is under specified value.
.
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)
• Heated oxygen sensor heater (front) monitor
• Misfire monitor
• Fuel system 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
• Accelerator pedal position sensor
.
AK303070
LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)
CONNECTOR: B-25
B-25 (B)
AB
AK303013
CONNECTORS: B-21, B-22
PCM
AB
AIR CLEANER
B-22 (B)
B-21 (B)
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>
13B-337
DTC SET CONDITIONS
Logic Flow Chart
.
Check Conditions
• Engine coolant temperature is higher than 50°C
(122
°F).
• Engine speed is between 1,250 and 3,000 r/min.
• Volumetric efficiency is between 18 and 60 per-
cent.
• Under the closed loop air/fuel control.
• The accelerator pedal open.
• Short-term fuel trim is at between −30 and +25
percent.
• More than 3 seconds have elapsed after the
abovementioned conditions have been met.
Judgment Criteria
• The left bank heated oxygen sensor (front) sends
"lean" and "rich" signals alternately 13 times or
less for 12 seconds.
NOTE: If the sensor switching frequency is lower
than the Judgment Criteria due to the MUT-III OBD-II
test Mode
−
H02S Test Results, it is assumed that
the heated oxygen sensor has deteriorated. If it is
higher, it is assumed that the harness is damaged or
has a short circuit.
If the heated oxygen sensor signal voltage has not
changed even once (lean/rich) after the DTC was
erased, the sensor switch time will display as 0 sec-
onds.
.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function
− OBD-II Drive Cycle −
Procedure 4
− Heated Oxygen Sensor Monitor
.
.
F0: THRESHOLD VALUE FOR AVERAGE SWITDHING FREQUENCY
START
MONITORING
CONDITIONS
MALFUNCTION
GOOD
END
NO
NO
YES
YES
Ff < F0
CALCULATE AVERAGE SWITCHING
FREQUENCY (Ff) OVER SPECIFIED TIMES
AK302395
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>
13B-338
TROUBLESHOOTING HINTS (The most
likely causes for this code to be set are: )
• Left bank heated oxygen sensor (front) deterio-
rated.
• 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
• MD998464: Test Harness
STEP 1. Using scan tool MB991958, check data list item 11:
Heated Oxygen Sensor Bank 2, Sensor 1 (left front).
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
11, Heated Oxygen Sensor Bank 2, Sensor 1 (left front).
(4) Warm up the engine, 2,500 r/min.
• Output voltage repeats 0.4 volt or less and 0.6 − 1.0 volt
10 times or more within 10 seconds.
(5) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
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 Malfunctions
.
AC305412
AB
MB991910
DATA LINK
CONNECTOR
MB991824
MB991827
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>
13B-339
STEP 2. Check the left bank heated oxygen sensor (front).
(1) Disconnect the left bank heated oxygen sensor (front)
connector B-25 and connect test harness special tool,
MD998464, to the connector on the left bank heated oxygen
sensor (front) side.
(2) Warm up the engine until engine coolant temperture
reaches 80
°C (176°F) or higher.
(3) Perform a racing for 5 minutes or more with the engine
speed of 4,500 r/min.
(4) Connect a digital voltage meter between terminal No. 2
(black clip) and terminal No. 4 (white clip).
(5) While repeatedly revving the engine, measure the left bank
heated oxygen sensor (front) output voltage.
Standard value: 0.6
− 1.0 volt
CAUTION
• Be very careful when connecting the jumper wires;
incorrect connection can damage the heated oxygen
sensor.
• Be careful the heater is broken when voltage of beyond
8 volts is applied to the heated oxygen sensor heater.
NOTE: If the sufficiently high temperature [of approximate
400
°
C (752
°
F) or more] is not reached although the heated
oxygen sensor is normal, the output voltage would be possi-
bly low although the rich air/fuel ratio. Therefore, if the out-
put voltage is low, use a jumper wire to connect the terminal
No.1 (red clip) and the terminal No. 3 (blue clip) of the
heated oxygen sensor with the positive terminal and the
negative terminal of 8 volts power supply respectively, then
check again.
Q: Is the voltage between 0.6 and 1.0 volt?
YES : Go to Step 3.
NO : Replace the left bank heated oxygen sensor (front).
Then go to Step 4.
AK303071
1
2
3
4
LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)
CONNECTOR: B-25
B-25 (B)
AB
HARNESS
CONNECTOR:
COMPONENT SIDE
AKX01624
HEATED
OXYGEN
SENSOR
COMPONENT
SIDE
CONNECTOR
MD998464
WHITE
BLACK
AQ
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