Mitsubishi Galant (2004+). Manual - part 1161

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-337

DTC SET CONDITIONS

Logic Flow Chart

.

• 20 seconds or more have passed since the 

engine starting sequence was completed.

• Engine coolant temperature is higher than 76°C 

(169

° F).

• Engine speed is higher than 1,200 r/min.

• Volumetric efficiency is higher than 30 percent.

• Throttle position sensor output voltage is lower 

than 4 volts.

• Except while fuel is being shut off.

• Monitoring time: 30 seconds.

Judgment Criteria

• Left bank heated oxygen sensor (front) output 

voltage does not get across 0.5 volt within about 
30 seconds.

.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function 

− OBD-II Drive Cycle − 

Procedure 6 

− Other Monitor 

P.13B-5

.

.

TROUBLESHOOTING HINTS (The most likely 
causes for this code to be set are: )

• Left bank heated oxygen sensor (front) deterio-

rated.

• Harness damage in left bank heated oxygen sen-

sor (front) output line.

• Left bank heated oxygen sensor (rear) deterio-

rated.
NOTE: When the left bank heated oxygen sensor 
(front) begins to deteriorate, the heated oxygen 
sensor output voltage will deviate from the volt-
age when the sensor was new (normally 0.5 volt 
at stoichiometric ratio). This deviation will be cor-
rected by the left bank heated oxygen sensor 
(rear).

HEATED OXYGEN SENSOR (FRONT) 

OUTPUT VOLTAGE CROSSES 0.5V?

START

END

NO

NO

NO

YES

Yes

YES

MALFUNCTION

GOOD

30secs HAVE PASSED?

MONITORING

CONDITIONS

AK203999

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-338

If the left bank heated oxygen sensor (rear) 
responds poorly because it has deteriorated, it 
will improperly correct the left bank heated oxy-
gen sensor (front). Thus, even when closed loop 
control is being effected, the fluctuation of the left 
bank heated oxygen sensor (front) output voltage 
decreases, without intersecting with 0.5 volt. As a 
result, there is a possibility of DTC P0154 becom-
ing registered.

• Open circuit in left bank injector.

• Harness damage in left bank 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

• MD998464: Test Harness

STEP 1. Using scan tool MB991958, check data list item 59: 
Heated Oxygen Sensor Bank 2, Sensor 2 (left 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 

59, Heated Oxygen Sensor Bank 2, Sensor 2 (left 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 P0156 

− Heated Oxygen Sensor Circuit 

(bank 2, sensor 2) 

P.13B-359

, DTC P0157 

− Heated 

Oxygen Sensor Circuit Low Voltage (bank 2, sensor 
2) 

P.13B-377

, DTC P0158-Heated Oxygen Sensor 

Circuit High Voltage (bank 2, sensor 2) 

P.13B-384

, 

DTC P0159 

− Heated Oxygen Sensor Circuit Slow 

Response (bank 2, sensor 2) 

P.13B-389

. 

STEP 2. Check for exhaust leak.
Q: Are there any abnormalities?

YES : Repair it. Then go to Step 12.
NO :  Go to Step 3.

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 3. Check for intake system vacuum leak.
Q: Are there any abnormalities?

YES : Repair it. Then go to Step 12.
NO :  Go to Step 4.

STEP 4. Check harness connector B-25 at the left bank 
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 

Connector Inspection 

P.00E-2

. Then go to Step 12.

AK303071

1

2

3

4

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

CONNECTOR: B-25

B-25 (B)

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-340

STEP 5. 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 80

°C (176°F) or 

higher.

(3) Perform a tracing for 5 minutes or more with the engine 

speed of 4,500 r/min.

(4) Connect a digital volt 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 wire; 

incorrect connection can damage the oxygen sensor.

• Be careful the heater is broken when voltage of beyond 

8V is applied to the oxygen sensor heater.
NOTE: If the sufficiently high temperature (of approximate 
400

°

C or more) is not reached although the oxygen sensor 

is normal, the output voltage would be possibly low 
although the rich air-fuel ratio. Therefore, if the output volt-
age is low, use a jumper wire to connect the terminal No.1 
(red clip of special tool) and the terminal No. 3 (blue clip of 
special tool) of the oxygen sensor with a (+) terminal and (-) 
terminal of 8 V power supply respectively, then check again.

Q: Is the voltage between 0.6 and 1.0 volt?

YES : Go to Step 6.
NO :  Replace the left bank heated oxygen sensor (front). 

Then go to Step 12.

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