Mitsubishi Lancer Evolution X. Manual - part 389

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-621

DIAGNOSIS

Required Special Tools:

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: V.C.I.
• MB991827: USB Cable
• MB991910: Main Harness A

STEP 1. Using scan tool MB991958, read the diagnostic 
trouble code (DTC).

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) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC P0461 set?

YES :  Go to Step 2.
NO :  Go to Step 4.

STEP 2. Check fuel gauge.
Q: Is the fuel gauge functioning?

YES :  Go to Step 3.
NO :  Refer to GROUP 54A, Combination Meter − Trouble 

Symptom Chart 

P.54A-67

.

STEP 3. Check the trouble symptoms.
Check that the fuel gauge operates correctly.
Q: Does the fuel gauge operates correctly?

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.00-15

.

NO :  Replace the ECM. When the ECM is replaced, 

register the ID code. Refer to GROUP 42B, Diagnosis 
− ID Codes Registration Judgment Table <Vehicles 

with KOS> 

P.42B-11

 or GROUP 42C, Diagnosis − ID 

Codes Registration Judgment Table <Vehicles with 
WCM> 

P.42C-9

. Then go to Step 6.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-622

STEP 4. Check the fuel level sensor (sub).
Check to see if the fuel level sensor is normal. Refer to GROUP 
54A, Combination Meter − On-vehicle Service − Fuel Gauge Unit 

Check 

P.54A-99

.

Q: Is the fuel level sensor (sub) normal?

YES :  Go to Step 5.
NO :  Replace the fuel level sensor (sub). Then go to Step 

6.

STEP 5. Check the trouble symptoms.
Check that the fuel gauge operates correctly.
Q: Does the fuel gauge operates correctly?

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.00-15

.

NO :  Replace the ECM. When the ECM is replaced, 

register the ID code. Refer to GROUP 42B, Diagnosis 
− ID Codes Registration Judgment Table <Vehicles 

with KOS> 

P.42B-11

 or GROUP 42C, Diagnosis − ID 

Codes Registration Judgment Table <Vehicles with 
WCM> 

P.42C-9

. Then go to Step 6.

STEP 6. Check the trouble symptoms.
Check that the fuel gauge operates correctly.
Q: Does the fuel gauge operates correctly?

YES :  The inspection is complete.
NO :  Retry the troubleshooting.

DTC P2096: Post Catalyst Fuel Trim System too Lean

.

TECHNICAL DESCRIPTION

• The ECM effects air/fuel ratio feedback control in 

accordance with the signals from the heated oxy-
gen sensor (front).

• If the heated oxygen sensor (front) has deterio-

rated, corrections will be made by the heated 
oxygen sensor (rear).

.

DESCRIPTIONS OF MONITOR METHODS

• When an abnormality exists in the heated oxygen 

sensor (front), the amount of compensated fuel 
injection is abnormal. When this situation contin-
ues, it is judged to be faulty.

• If an abnormality exists in the heated oxygen sen-

sor (rear), also it is judged to be faulty even 
though the heated oxygen sensor (front) is nor-
mal.

.

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 (front) monitor
• Heated oxygen sensor (rear) monitor
• Heated oxygen sensor (front) heater monitor
• Heated oxygen sensor (rear) heater monitor
• Heated oxygen sensor (front) inactive monitor
• Heated oxygen sensor offset voltage monitor
• Misfire monitor
• Fuel system monitor
• Air/fuel ratio feedback monitor

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

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MULTIPORT FUEL INJECTION (MFI)

13A-623

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

.

DTC SET CONDITIONS

Logic Flow Chart

.

Check Conditions

• Engine coolant temperature is more than 76° C 

(169° F).

• Under the closed loop air/fuel control.

• More than 90 seconds have passed since the 

engine starting sequence was completed.

• Mass airflow sensor output is more than 5 g/sec.

End

Malfunction

No

No

No

D

LEAN

 >= D

0

D

LEAN

: Fuel trim based on heated oxygen sensor (rear) <to lean>

D

LEAN

: Fuel trim based on heated oxygen sensor (rear) <to rich>

D

0

: Maximum Limit of D

LEAN

D

1

: Maximum Limit of D

RICH

D

RICH

 >= D

1

Good

AK900364

No

Start

Yes

Yes

Yes

Yes

Continuous
failure for 5secs

Monitoring
conditions

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-624

Judgement Criterion

• The amount of compensated rich air/fuel ratio is 

output by the heated oxygen sensor (rear). The 
status that the amount of compensated rich 
air/fuel ratio is greater than the specified amount 
continues for 5 seconds.

.

FAIL-SAFE AND BACKUP FUNCTION

• None

.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function − OBD-II Drive Cycle − 

Pattern 1 

P.13A-9

.

.

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

• Heated oxygen sensor (front) failed.
• Heated oxygen sensor (rear) failed.
• Injector failed.
• ECM failed.

DIAGNOSIS

Required Special Tools:

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: V.C.I.
• MB991827: USB Cable
• MB991910: Main Harness A

STEP 1. Using scan tool MB991958, read the diagnostic 
trouble code (DTC).

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) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the diagnostic trouble code other than P2096 set?

YES : Refer to, Diagnostic Trouble Code Chart 

P.13A-48

.

NO :  Go to Step 2. 

STEP 2. Replace the heated oxygen sensor (front).
(1) Replace the heated oxygen sensor (front).
(2) Carry out a test drive with the drive cycle pattern. Refer to 

Diagnostic Function − OBD-II Drive Cycle − Pattern 1 

P.13A-9

.

(3) Check the diagnostic trouble code (DTC).
Q: Is DTC P2096 set?

YES :  Go to Step 3. 
NO :  The inspection is complete.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB