Mitsubishi Lancer Evolution IX. Manual - part 390

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-35

Code No. P105: Barometric Pressure Sensor System

OPERATION

• A power voltage of 5 V is applied to the baromet-

ric pressure sensor power terminal (terminal No. 
1) of the air flow sensor connector from the 
engine-ECU (terminal No. 42) and earthed to the 
engine-ECU (terminal No. 34) from the air flow 
sensor (terminal No. 5).

• The sensor signal is inputted to the engine-ECU 

(terminal No. 51) from the barometric pressure 
sensor output terminal (terminal No. 2) of the air 
flow sensor connector.

FUNCTION

• The barometric pressure sensor converts the bar-

ometric pressure into a voltage signal and inputs 
the signal to the engine-ECU.

• In response to the signal, the engine-ECU cor-

rects the fuel injection amount, etc.

TROUBLE JUDGMENT

Check Condition

• 2 seconds after the ignition switch has been 

placed in the "ON" position or the engine has 
started up.

Judgment Criterion

• The sensor output voltage of 4.5 V or more (Baro-

metric pressure above 114 kPa or equivalent) for 

2 seconds.

or 

• The sensor output voltage 0.2 V or less (Baro-

metric pressure below 53 kPa or equivalent) for 2 

seconds.

PROBABLE CAUSES

• Failed barometric pressure sensor

• Open/short circuit in barometric pressure sensor 

circuit or loose connector contact

• Failed engine-ECU

7

4 5 6

1 2 3

AK501801

65

43
50

42
49

41
48
60 61

64

46 47
58 59
67 68

45

56
66

52

51

44

53

62

54

63

57

55

2

3 4

5 6

7 8

9

11 12 13 14 15 16 17 18 19 20

30

21 22 23

24 25

26 27 28 29

3132 33

34 35

1

10

5 V

Engine-ECU

42

GR

Y-L

B

51

34

Barometric pressure sensor 
(Incorporated in air flow sensor)

1

2

5

Barometric pressure sensor circuit

Wire colour code
B: Black  LG: Light green  G: Green  L: Blue  W: White  Y: Yellow  SB: Sky blue  BR: Brown  O: Orange  GR: Gray
R: Red  P: Pink  V: Violet  PU: Purple

AB

B-105 

(MU802552)

C-119 

(MU803782)

C-121 

(MU803783)

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-36

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-II/III data list

• Refer to Data List Reference Table 

P.13A-372

.

a. Item No. 25: Barometric pressure sensor

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use 

Troubleshooting/Inspection Service Points 

P.00-5

).

NO : 

Go to Step 2 .

STEP 2. Connector check: B-105 air flow sensor 
connector

Q: Is the check result normal?

YES : 

Go to Step 3 .

NO : 

Repair or replace the connector.

STEP 3. Perform voltage measurement at B-105 
air flow sensor connector.

• Disconnect connector, and measure at harness 

side.

• Ignition switch: "ON"

• Voltage between terminal No. 1 and earth.

OK: 4.9 

− 5.1 V

Q: Is the check result normal?

YES : 

Go to Step 9 .

NO : 

Go to Step 4 .

STEP 4. Perform voltage measurement at C-119 
engine-ECU connector.

• Measure engine-ECU terminal voltage.

• Ignition switch: "ON"

• Voltage between terminal No. 42 and earth.

OK: 4.9 

− 5.1 V

Q: Is the check result normal?

YES : 

Go to Step 5 .

NO : 

Go to Step 6 .

AK305005

3

4

5

1

2

6

7

AB

Connector : B-105

Harness side 
connector

B-105(B)

AK305005

3

4

5

1

2

6

7

AB

Connector : B-105

Harness side 
connector

B-105(B)

AK501994

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43
50

42
49

41
48
60

61

64

46

47

58

59

67

68

45

56
66

52 51

44

53

62

54

63

57

55

AB

Connector: C-119

C-119 (GR)

C-119 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-37

STEP 5. Connector check: C-119 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Check and repair harness between B-105 

(terminal No. 1) air flow sensor connector 
and C-119 (terminal No. 42) engine-ECU 
connector.

• Check power supply line for open 

circuit.

NO : 

Repair or replace the connector.

STEP 6. Connector check: C-119 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 7 .

NO : 

Repair or replace the connector.

AK501994

65

43
50

42
49

41
48
60

61

64

46

47

58

59

67

68

45

56
66

52 51

44

53

62

54

63

57

55

AB

Connector: C-119

C-119 (GR)

C-119 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

AK305005

3

4

5

1

2

6

7

AB

Connector : B-105

Harness side 
connector

B-105(B)

AK501994

65

43
50

42
49

41
48
60

61

64

46

47

58

59

67

68

45

56
66

52 51

44

53

62

54

63

57

55

AB

Connector: C-119

C-119 (GR)

C-119 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI)

13A-38

STEP 7. Check harness between B-105 (terminal 
No. 1) air flow sensor connector and C-119 
(terminal No. 42) engine-ECU connector.

• Check power supply line for short circuit.

Q: Is the check result normal?

YES : 

Go to Step 8 .

NO : 

Repair the damaged harness wire.

STEP 8. M.U.T.-II/III data list

• Refer to Data List Reference Table 

P.13A-372

.

a. Item No. 25: Barometric pressure sensor

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use 

Troubleshooting/Inspection Service Points 

P.00-5

).

NO : 

Replace the engine-ECU.

STEP 9. Perform resistance measurement at 
B-105 air flow sensor connector.

• Disconnect connector, and measure at harness 

side.

• Resistance between terminal No. 5 and earth.

OK: 2 

Ω or less

Q: Is the check result normal?

YES : 

Go to Step 12 .

NO : 

Go to Step 10 .

AK305005

3

4

5

1

2

6

7

AB

Connector : B-105

Harness side 
connector

B-105(B)

AK501994

65

43
50

42
49

41
48
60

61

64

46

47

58

59

67

68

45

56
66

52 51

44

53

62

54

63

57

55

AB

Connector: C-119

C-119 (GR)

C-119 (GR)

Harness side connector

<L. H. drive vehicles>

<R. H. drive vehicles>

AK305005

3

4

5

1

2

6

7

AB

Connector : B-105

Harness side 
connector

B-105(B)