Mitsubishi Galant 9G. Manual - part 983

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-232

DTC SET CONDITIONS

Logic Flow Chart

.

Check Conditions

• 20 seconds or more have passed since the 

engine starting sequence was completed.

• Engine coolant temperature is higher than 50°C 

(122

°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

• Right 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-6

.

.

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-233

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

• Right bank heated oxygen sensor (front) deterio-

rated.

• Harness damage in right bank heated oxygen 

sensor (front) output line.

• Right bank heated oxygen sensor (rear) deterio-

rated.
NOTE: When the right bank heated oxygen sen-
sor (front) begins to deteriorate, the heated oxy-
gen 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 right bank heated oxygen sensor 
(rear).

If the right bank heated oxygen sensor (rear) 
responds poorly because it has deteriorated, it 
will improperly correct the right bank heated oxy-
gen sensor (front). Thus, even when closed loop 
control is being effected, the fluctuation of the 
right bank 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 right bank injector.

• Harness damage in right 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 69: 
Heated Oxygen Sensor Bank 1, Sensor 2 (right 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, Heated Oxygen Sensor Bank 1, Sensor 2 (right 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 

− Heated Oxygen Sensor Circuit 

(bank 1, sensor 2) DTC 

P.13B-255

, P0137 

− Heated 

Oxygen Sensor Circuit Low Voltage (bank 1, sensor 
2) 

P.13B-273

, DTC P0138 

− Heated Oxygen Sensor 

Circuit High Voltage (bank 1, sensor 2) 

P.13B-280

, 

DTC P0139 

− Heated Oxygen Sensor Circuit Slow 

Response (bank 1, sensor 2) 

P.13B-285

. 

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-234

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

YES : Repair it. Then go to Step 13.
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 13.
NO :  Go to Step 4.

STEP 4. Check harness connector B-09 at the right 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 13.

1

2

3

4

AK303048

B-09 (B)

CONNECTOR: B-09

THROTTLE BODY

RIGHT BANK
HEATED OXYGEN
SENSOR (FRONT)

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI) <3.8L ENGINE>

13B-235

STEP 5. Check the right bank heated oxygen sensor 
(front).

(1) Disconnect the right bank heated oxygen sensor (front) 

connector B-09 and connect test harness special tool, 
MD998464, to the connector on the right bank 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 right 

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 6.
NO :  Replace the right bank heated oxygen sensor (front). 

Then go to Step 13.

1

2

3

4

AK303048

B-09 (B)

CONNECTOR: B-09

THROTTLE BODY

RIGHT BANK
HEATED OXYGEN
SENSOR (FRONT)

AB

HARNESS
CONNECTOR:
COMPONENT SIDE

AKX01624

HEATED
OXYGEN
SENSOR
COMPONENT
SIDE
CONNECTOR

MD998464

WHITE

BLACK

AQ