Mitsubishi Lancer Evolution IX. Manual - part 309

TROUBLESHOOTING

REAR AXLE

27-11

DIAGNOSTIC TROUBLE CODE 
PROCEDURES

Code No.71: Proportioning valve <AYC> system

4WD-ECU

PROPORTIONING
VALVE

DIRECTION
VALVE (LH)

DIRECTION
VALVE (RH)

FOR AYC
CONTROL

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   

Proportioning valve system/direction valve system circuit

18

3

16

15

14

1 2

17

4 5

8

20

19

6 7

2122

9 10

25

13

24

23

12

11

2

1

3

13

12

14

21

10

5

4

6

16

15

17

7 8 9

19

18

20

11

22

OPERATION

• After processing information of various sensors 

and switches, the 4WD-ECU calculates the 
amount of AYC torque movement and direction, 
and controls the proportioning valve.

• The current flows from the 4WD-ECU to activate 

the proportioning valve, which controls oil pres-
sure supplied to the AYC clutches.

DIAGNOSIS CODE SET CONDITIONS

Diagnosis code No.71 is set when the proportioning 
valve control circuit is open circuited or 
short-circuited.

PROBABLE CAUSES

• Malfunction of the proportioning valve

• Damaged harness wires and connectors

• Malfunction of the 4WD-ECU

TROUBLESHOOTING

REAR AXLE

27-12

DIAGNOSIS

STEP 1. M.U.T.-II/III data list
Set M.U.T.-II/III to data reading mode, and check the 
data list item.
Item 12: Proportioning valve current <AYC> (Refer to 
Data List Table 

P.22A-142

). 

Q: Is the check result normal?

YES : 

This malfunction is intermittent. Refer to 

GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

− 

How to Cope with Intermittent Malfunction 

P.00-5

.

NO : 

Go to Step 2.

STEP 2. Measure the resistance at  proportioning 
valve connector F-25.

AC310716

1

3

2

Connector: F-25

F-25 (3-B)

AB

Hydraulic unit
assembly

Disconnect the connector, and measure the resist-
ance between terminal 2 and 3 at the proportioning 
valve side.

OK: 4.7 

Ω or less

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Replace the hydraulic unit.

STEP 3.  Measure the resistance at  
proportioning valve connector F-25.

AC310718

3

1

2

Connector: F-25

F-25 (3-B)

AB

Hydraulic unit
assembly

Harness
side

Measure the resistance between terminal 2 and 
earth at the wiring harness side.

OK: 2 

Ω or less

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Repair the defective connector.

STEP 4.  Connectors check: F-25 proportioning 
valve connector, F-21 intermediate connector

AC310718

3

1

2

Connector: F-25

F-25 (3-B)

AB

Hydraulic unit
assembly

Harness
side

7

3

5

1

6

2

8

4

AC310719AB

Connector: F21

F-21 (8-B)

Check for the contact with terminals.

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the defective connector.

TROUBLESHOOTING

REAR AXLE

27-13

STEP 5. Check the harness wires between 
proportioning valve connector F-25 terminal 2 
and intermediate connector F-21 terminal 4 and 
earth.

AC310718

3

1

2

Connector: F-25

F-25 (3-B)

AB

Hydraulic unit
assembly

Harness
side

7

3

5

1

6

2

8

4

AC310719AB

Connector: F21

F-21 (8-B)

Check the earth line for open circuit.

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Repair the wiring harness.

TROUBLESHOOTING

REAR AXLE

27-14

STEP 6. Connectors check: C-25 4WD-ECU 
connector, C-124, C-134 and F-21 intermediate 
connectors, and F-25 proportioning valve 
connector

AC310721

18

16

1415

17

23

21

1920

22

26

2425

3

1 2

4 5

10

8

6 7

9

13

12

11

4WD-ECU

C-25 (26-Y)

Connector: C-25

AB

AC310722

18

3

16

15

14

1 2

17

4 5

8

20

19

6 7

2122

9 10

25

13

24

23

12

11

Connector: C-124
<LHD>

AB

C-124 (25)

AC310738

18

3

16

15

14

1 2

17

4 5

8

20

19

6 7

2122

9 10

25

13

24

23

12

11

Connector: C-124
<RHD>

AB

C-124 (25)

AC310723

6

2

5

1

7 8

11

4

9 10

3

Connector: C-134
<LHD>

AB

C-134 (11-B)

AC310726

6

2

5

1

7 8

11

4

9 10

3

Connector: C-134
<RHD>

AB

C-134 (11-B)

AC310718

3

1

2

Connector: F-25

F-25 (3-B)

AB

Hydraulic unit
assembly

Harness
side

7

3

5

1

6

2

8

4

AC310719AB

Connector: F21

F-21 (8-B)

Check for the contact with terminals.

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Repair the defective connector.