Mitsubishi Lancer Evolution X. Manual - part 299

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-261

Check Conditions

• Engine coolant temperature is higher than 76° C 

(169° F).

• The heated oxygen sensor (front) is active.
• The cumulative mass airflow sensor output is 

1,638 g or higher.

• Fuel is being shut off.
• Heated oxygen sensor (rear) output voltage is 0.5 

volt or higher when fuel cut is started.

• It has been taking more than 180 seconds since 

the drive signal of the heated oxygen sensor 
(rear) heater was turned on.

• Barometric pressure is higher than 76 kPa (22.4 

in.Hg).

Judgement Criterion

• Heated oxygen sensor (rear) output voltage does 

not reach 0.2 volt for 6.0 seconds from fuel cut 
start.

Check Conditions

• Engine coolant temperature is higher than 76° C 

(169° F).

• The heated oxygen sensor (front) is active.
• The cumulative mass airflow sensor output is 

1,638 g or higher.

• Fuel is being shut off.
• The heated oxygen sensor (rear) output voltage 

is higher than 0.5 volt when fuel cut is started.

• It has been taking more than 180 seconds since 

the drive signal of the heated oxygen sensor 
(rear) heater was turned on.

• Barometric pressure is higher than 76 kPa (22.4 

in.Hg).

• The ECM monitors for this condition for 3 cycles 

of 0.5 second each during drive cycles.

Judgement Criteria

• The heated oxygen sensor (rear) output voltage 

does not reach 0.2 volt for 0.5 second from 0.4 
volt while fuel is being shut off.

• The ECM monitors for this condition once during 

the drive cycle.

.

NOTE: Monitoring stops after fuel has been shut off 
for 64 seconds or more.

.

FAIL-SAFE AND BACKUP FUNCTION

• None

.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function − OBD-II Drive Cycle − 

Pattern 10 

P.13A-9

.

.

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

• Heated oxygen sensor (rear) deteriorated.
• Connector damage.
• ECM failed. 

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-262

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, check data list item 
AD: 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 

AD, Heated Oxygen Sensor (rear).

(4) Warm up the engine.

• After increasing the output voltage 0.5 volt or more by 

the engine revving, finish it. Then confirm that the output 
voltage reduces to 0.2 volt or less within 6 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.00-15

.

NO :  Replace the heated oxygen sensor (rear). Then go to 

Step 2. 

STEP 2. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to 

Diagnostic Function − OBD-II Drive Cycle − Pattern 10 

P.13A-9

.

(2) Check the diagnostic trouble code (DTC).
Q: Is DTC P0139 set?

YES : Refer to DTC P0137 − Heated Oxygen Sensor (rear) 

Circuit Low Voltage 

P.13A-246

, DTC P0138 − Heated 

Oxygen Sensor (rear) Circuit High Voltage 

P.13A-254

.

NO :  The inspection is complete.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-263

DTC P0140: Heated Oxygen Sensor (rear) Circuit  No Activity Detected

AK704250

1 2
3 4

1

2

3 4 5 6 7 8 9 10 11 12 13 14 15 16

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

2

8

7

6

5

4

3

11

21

20

19

18

17

16

15

14

13

12

9

22

1

10

1

2

3 4 5 6

AB

D-35

FROM MFI RELAY

TO ECM

1

4

2

3

HEATED OXYGEN SENSOR (REAR) CIRCUIT

HEATED OXYGEN
SENSOR (REAR)

B-09

YELLO

W

ORANGE

ORANGE

YELLO

W

ENGINE
CONTROL
MODULE

0.5 V

C-45

3

41

40

2

ORANGE

YELLO

W

6

5

A-13

AK704229AB

Connector: A-13

A-13

AK704227

Connector: B-09

ECM

B-09 (GR)

AB

AK704251

Connector: C-45

C-45

AB

MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS

TSB Revision

MULTIPORT FUEL INJECTION (MFI)

13A-264

.

CIRCUIT OPERATION

• A voltage corresponding to the oxygen concen-

tration in the exhaust gas is sent to the ECM (ter-
minal No. 40) from the output terminal (terminal 
No. 3) of the heated oxygen sensor (rear).

• Terminal No. 4 of the heated oxygen sensor 

(rear) is grounded with ECM (terminal No. 41).

• The ECM applies an offset voltage of 0.5 volt to 

terminal No. 4 of the heated oxygen sensor 
(rear).

.

TECHNICAL DESCRIPTION

• The output signal of the heated oxygen sensor 

(front) is compensated by the output signal of the 
heated oxygen sensor (rear).

• The ECM checks for the heated oxygen sensor 

(rear) output voltage.

.

DESCRIPTIONS OF MONITOR METHODS

Heated oxygen sensor (rear) output voltage does not 

change during specified go/stop operations 
including fuel cut are repeated.

.

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

Sensor (The sensor below is determined to be 

normal)

• Mass airflow sensor
• Engine coolant temperature sensor
• Intake air temperature sensor
• Barometric pressure sensor

.

AK704232

Heated oxygen
sensor (rear)

Connector: D-35

D-35 (B)

AB

Rear heater
duct