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)

AK303013

CONNECTORS: B-21, B-22

PCM

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

P.13B-6

F0: THRESHOLD VALUE FOR AVERAGE SWITDHING FREQUENCY

START

MONITORING

CONDITIONS

MALFUNCTION

GOOD

END

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

P.00-14

NO : Go to Step 2.

AC305412

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

LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)

CONNECTOR: B-25

B-25 (B)

HARNESS
CONNECTOR:
COMPONENT SIDE

AKX01624

HEATED
OXYGEN
SENSOR
COMPONENT
SIDE
CONNECTOR

MD998464

WHITE

BLACK

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