Mitsubishi Galant 9G. Manual — part 719
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-318
.
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 cylinder 2, 3 heated oxygen sensor
(front).
• Terminal No. 2 of the cylinder 2, 3 heated oxygen
sensor (front) is grounded with PCM (terminal
No. 69).
.
TECHNICAL DESCRIPTION
• The cylinder 2, 3 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 cylinder 2, 3 heated oxygen sensor
(front) begins to deteriorate, the 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 cylinder 2, 3 heated oxy-
gen sensor (front). In addition, the PCM also
checks for an open circuit in the cylinder 2, 3
heated oxygen sensor (front) output line.
.
DESCRIPTIONS OF MONITOR METHODS
Cylinder 2, 3 heated oxygen sensor (front) output
voltage stays low when air/fuel ratio is forced to
be rich. The above procedure is repeated when
oxygen sensor is inactive.
.
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
.
AK303829AB
CONNECTOR: B-36
B-36 (GR)
CYLINDER 2, 3
HEATED OXYGEN
SENSOR (FRONT)
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) <2.4L ENGINE>
13A-319
DTC SET CONDITIONS
Logic Flow Chart
.
Check Conditions
• After 2 seconds or more pass from the time when
the monitor determines normally for detecting an
open circuit.
• Cylinder 2, 3 heated oxygen sensor (front) signal
voltage has continued to be 0.2 volt or lower.
• Engine coolant temperature is higher than 76°C
(169
°F).
• Mass airflow sensor output is 6 g/sec or more.
• At least 20 seconds have passed since fuel shut
off control was canceled.
• Monitoring time: 8 seconds.
START
V
F
> =4.5V
2secs HAS PASSED
YES
YES
YES
NO
NO
NO
MALFUNCTION
MONITORING
CONDITIONS
YES
NO
MONITORING
CONDITIONS
+5V ON
AK401409
V
F
< 0.2V
8secs HAS PASSED
YES
YES
NO
NO
END
MALFUNCTION
GOOD
MODULATE A/F CONDITION TO RICH
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-320
Judgement Criteria
• Making the air/fuel ratio 15 percent richer for 8
seconds does not result in raising the heated oxy-
gen sensor (front) output voltage beyond 0.2 volt.
.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function
− OBD-II Drive Cycle −
Procedure 6
− Other Monitor
.
TROUBLESHOOTING HINTS (The most
likely causes for this code to be set are:)
• Cylinder 2, 3 heated oxygen sensor (front) failed.
• Short circuit in cylinder 2, 3 heated oxygen sen-
sor (front) output line.
• 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:
Cylinder 2, 3 Heated Oxygen Sensor (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, Cylinder 2, 3 Heated Oxygen Sensor (front).
• Warm up the engine. When the engine is revved, the
output voltage should measure 0.6 to 1.0 volt.
• Warm up the engine. When the engine is idling, the out-
put voltage should repeat 0.4 volt and 0.6 to 1.0 volt
alternately.
(4) 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
.
NO : Go to Step 2.
AK303804AB
MB991910
DATA LINK
CONNECTOR
MB991824
MB991827
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-321
STEP 2. Check the cylinder 2, 3 heated oxygen sensor
(front).
(1) Disconnect the cylinder 2, 3 heated oxygen sensor (front)
connector B-36 and connect test harness special tool
MB991316 to the connector on the cylinder 2, 3 heated
oxygen sensor (front) side.
(2) Warm up the engine until engine coolant temperature
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 cylinder
2, 3 heated oxygen sensor 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 measured voltage between 0.6 and 1.0 volt?
YES : Go to Step 3.
NO : Replace the cylinder 2, 3 heated oxygen sensor
(front). Then go to Step 5.
AK303830
1
2
3
4
AB
CONNECTOR: B-36
B-36 (GR)
CYLINDER 2, 3
HEATED OXYGEN
SENSOR (FRONT)
HARNESS
CONNECTOR:
COMPONENT SIDE
AKX01624
HEATED
OXYGEN
SENSOR
COMPONENT
SIDE
CONNECTOR
MB991316
WHITE
BLACK
AN
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