Mitsubishi Galant (2004+). Manual - part 689

AUTOMATIC TRANSAXLE DIAGNOSIS

TSB Revision

AUTOMATIC TRANSAXLE

23A-307

STEP 2. Check the shift points.
Q: Are the shift points early or late only when transmission 

fluid is -29

°C (84°F) or less (early), or 125°C (257°F) or 

more (late)?
YES : The symptom is due to characteristics of the 

INVECS-II system, but is not abnormal.

NO :  Go to Step 3.

STEP 3. Disassemble and clean the valve body.

Check the O-ring installation bolts for looseness and the valve 
body for damage. Repair or replace the faulty parts. Refer to 
GROUP 23B, Valve Body 

P.23B-79

.

Replace the valve body assembly if the damages are thought 
to be irreparable. Then check the symptom.
Q: Is the symptom eliminated?

YES : The procedure is complete.
NO :  Go to Step 4.

STEP 4. Replace the PCM.
Q: Is the symptom eliminated?

YES : The procedure is complete.
NO :  Start over at Step 1.

INSPECTION PROCEDURE 12: No Diagnostic Trouble Codes (Does not Shift)

AC001860 AB

VALVE
BODY
ASSEMBLY

POWERTRAIN 
CONTROL 
MODULE

RELAY 
BOX

BATTERY

BATTERY 
BACKUP

AC210058AC

Backup Power Supply System Circuit

AUTOMATIC TRANSAXLE DIAGNOSIS

TSB Revision

AUTOMATIC TRANSAXLE

23A-308

.

CIRCUIT OPERATION
PCM (terminal number 42) receives battery positive 
voltage from the battery.

.

COMMENT
If shifting does not occur while driving and no diag-
nostic trouble codes are output, a malfunction of the 
transmission range switch, or PCM may exist.

.

TROUBLESHOOTING HINTS (The most likely 
causes for this condition:)

• Malfunction of the transmission range switch

• Damaged harness, connector

• Malfunction of the PCM

DIAGNOSIS

Required Special Tool:

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: V.C.I.

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A

STEP 1. Check the vehicle acceleration.
Q: Does the vehicle accelerate poorly (transaxle stays in 

3rd gear) when starting from a stop with the selector 
lever in "D" range?
YES : Go to Step 2.
NO :  Go to Step 5.

AC306248AH

CONNECTOR: B-20

PCM

AIR
CLEANER

JAE

41

37

32

40

39

23

21 22

35

31

30

26

36

27

43

42

25

24

38

34

29

33

28

B-20

AUTOMATIC TRANSAXLE DIAGNOSIS

TSB Revision

AUTOMATIC TRANSAXLE

23A-309

STEP 2. Measure the backup power supply voltage at PCM 
connector B-20 by using check harness special tool 
MB991923.

(1) Disconnect all the connectors from the PCM.

(2) Connect special tool MB991923 (check harness) between 

the PCM and the body-side harness connector.

(3) Turn the ignition switch to the "ON" position.

AC306248AH

CONNECTOR: B-20

PCM

AIR
CLEANER

JAE

41

37

32

40

39

23

21 22

35

31

30

26

36

27

43

42

25

24

38

34

29

33

28

B-20

AC209793AK

SPECIAL TOOL 23-PIN CONNECTOR
WITHOUT RED TAPE
(PCM CONNECTOR B-20)

B-20 
(GR)

25

21

24 23 22

29 28 27 26

34 33 32 31 30

38 37 36 35

43 42 41 40 39

PCM

MB991923

BODY SIDE
HARNESS

AUTOMATIC TRANSAXLE DIAGNOSIS

TSB Revision

AUTOMATIC TRANSAXLE

23A-310

(4) Measure the voltage between terminal 42 and ground.

• The voltage should measure battery positive voltage.

(5) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage battery positive voltage?

YES : Go to Step 5.
NO :  Go to Step 3.

STEP 3. Check PCM connector B-20 for loose, corroded or 
damaged terminals, or terminals pushed back in the 
connector.

Q: Is the connector in good condition?

YES : Go to Step 4.
NO :  Repair or replace the damaged components. Refer to 

GROUP 00E, Harness Connector Inspection 

P.00E-2

. Then retest the system.

AC210720

24

33

37

42

43

25

34

38

29

40

41

39

21

30

22

23

27

36

32

28

31

35

26

JAE

AC

B-20 HARNESS 
CONNECTOR: 
COMPONENT SIDE

AC306248AH

CONNECTOR: B-20

PCM

AIR
CLEANER

JAE

41

37

32

40

39

23

21 22

35

31

30

26

36

27

43

42

25

24

38

34

29

33

28

B-20