Mitsubishi Galant 9G. Manual — part 697
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-230
TROUBLESHOOTING HINTS (The most
likely causes for this code to be set are: )
• Cylinder 1, 4 heated oxygen sensor (front) deteri-
orated.
• Harness damage in cylinder 1, 4 heated oxygen
sensor (front) output line.
• Cylinder 1, 4 heated oxygen sensor (rear) deteri-
orated.
NOTE: When the cylinder 1, 4 heated oxygen
sensor (front) begins to deteriorate, the heated
oxygen sensor output voltage will deviate from
the voltage when the sensor was new (normally
0.5 volt at stoichiometric ratio). This deviation will
be corrected by the cylinder 1, 4 heated oxygen
sensor (rear).
If the cylinder 1, 4 heated oxygen sensor (rear)
responds poorly because it has deteriorated, it
will improperly correct the cylinder 1, 4 heated
oxygen sensor (front). Thus, even when closed
loop control is being effected, the fluctuation of
the cylinder 1, 4 heated oxygen sensor (front)
output voltage decreases, without intersecting
with 0.5 volt. As a result, there is a possibility of
DTC P0134 becoming registered.
• Open circuit in cylinder 1, 4 injector.
• Harness damage in cylinder 1, 4 injector circuit.
• Connector damage.
• PCM failed.
• Exhaust leak.
• Air drawn in from gaps in gasket, seals, etc.
• Incorrect fuel pressure.
DIAGNOSIS
Required Special Tools:
• MB991958: Scan Tool (MUT-III Sub Assembly)
• MB991824: V.C.I.
• MB991827: USB Cable
• MB991910: Main Harness A
• MB991316: Test Harness
STEP 1. Using scan tool MB991958, check data list item 69:
Cylinder 1, 4 Heated Oxygen Sensor (rear).
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
69, Cylinder 1, 4 Heated Oxygen Sensor (rear).
• Warming up the engine. When the engine is revved, the
output voltage should repeat 0 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 : Go to Step 2.
NO : Refer to DTC P0136
− Cylinder 1, 4 Heated Oxygen
Sensor Circuit (sensor 2)
, DTC P0137
−
Cylinder 1, 4 Heated Oxygen Sensor Circuit Low
Voltage (sensor 2)
, DTC P0138
− Cylinder
1, 4 Heated Oxygen Sensor Circuit High Voltage
(sensor 2)
, DTC P0139
− Cylinder 1, 4
Heated Oxygen Sensor Circuit Slow Response
(sensor 2)
AK303804AB
MB991910
DATA LINK
CONNECTOR
MB991824
MB991827
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
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STEP 2. Check for exhaust leak.
Q: Are there any abnormalities?
YES : Repair it. Then go to Step 11.
NO : Go to Step 3.
STEP 3. Check for intake system vacuum leak.
Q: Are there any abnormalities?
YES : Repair it. Then go to Step 11.
NO : Go to Step 4.
STEP 4. Check harness connector B-37 at the cylinder 1, 4
heated oxygen sensor (front) for damage.
Q: Is the harness connector in good condition?
YES : Go to Step 5.
NO : Repair or replace it. Refer to GROUP 00E, Harness
. Then go to Step 11.
AK303821
1
2
3
4
AB
CONNECTOR: B-37
CYLINDER 1, 4
HEATED OXYGEN
SENSOR (FRONT)
B-37 (GR)
HARNESS
CONNECTOR:
COMPONENT SIDE
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-232
STEP 5. Check the cylinder 1, 4 heated oxygen sensor
(front).
(1) Disconnect the cylinder 1, 4 heated oxygen sensor (front)
connector B-37 and connect test harness special tool
MB991316 to the connector on the cylinder 1, 4 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
1, 4 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 measured voltage between 0.6 and 1.0 volt?
YES : Go to Step 6.
NO : Replace the cylinder 1, 4 heated oxygen sensor
(front). Then go to Step 11.
AK303821
1
2
3
4
AB
CONNECTOR: B-37
CYLINDER 1, 4
HEATED OXYGEN
SENSOR (FRONT)
B-37 (GR)
HARNESS
CONNECTOR:
COMPONENT SIDE
AKX01624
HEATED
OXYGEN
SENSOR
COMPONENT
SIDE
CONNECTOR
MB991316
WHITE
BLACK
AN
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
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MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-233
STEP 6. Check harness connector B-01, B-27 at injector for
damage.
Q: Is the harness connector in good condition?
YES : Go to Step 7.
NO : Repair or replace it. Refer to GROUP 00E, Harness
. Then go to Step 11.
STEP 7. Check the cylinder 1, 4 injector.
(1) Disconnect each injector connector.
(2) Measure the resistance between injector side connector
terminal No. 1 and No. 2.
Standard value: 10.5
− 13.5 ohms [at 20°C (68°F)]
Q: Is the measured resistance between 10.5 and 13.5 ohms
[at 20
°C (68°F)]?
YES : Go to Step 8.
NO : Replace the injector. Then go to Step 11.
M
1
2
AK303822
B-01 (GR)
B-27 (GR)
CONNECTORS: B-01, B-27
AB
HARNESS CONNECTOR:
COMPONENT SIDE
M
1
2
AK303822
B-01 (GR)
B-27 (GR)
CONNECTORS: B-01, B-27
AB
HARNESS CONNECTOR:
COMPONENT SIDE
AK000559
2
1
INJECTOR SIDE
CONNECTOR
AB
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