Mitsubishi Galant. Manual — part 439

AUTOMATIC TRANSAXLE DIAGNOSIS

TSB Revision

AUTOMATIC TRANSAXLE

23A-223

INSPECTION PROCEDURE 4: Does not Move (forward or backward)

COMMENT
If the vehicle does not move forward or backward
when the selector lever is shifted to any position
while the engine is idling, the cause is probably
abnormal line pressure, or a malfunction of the
power train, oil pump or valve body.

TROUBLESHOOTING HINTS (The most likely

causes for this case:)

•

Abnormal line pressure

•

Malfunction of the power train

•

Malfunction of the oil pump

•

Malfunction of the valve body

•

Low A/T fluid level

•

Malfunction of the PCM

DIAGNOSIS

STEP 1. Check the hydraulic pressure.
Measure the hydraulic pressure of each element when the
transaxle is in 1st, 2nd or reverse. Check if each hydraulic
pressure is within the standard value. Refer to

P.23A-23

,

Hydraulic Pressure Test. If some elements are within the
standard value and some are not, recheck the symptom.

Q: Are all pressures within the standard value?

YES : Check A/T fluid level and condition. If not OK, repair

or replace as necessary, then recheck symptom. If
OK, go to Step 3.

NO : Go to Step 2.

STEP 2. Disassemble and clean the valve body.
Check the O-ring installation bolts for looseness and valve
body for damage. Repair or replace the faulty parts. Refer to
GROUP 23B, Valve Body

P.23B-68

.

Q: Is the repair possible and the symptom eliminated?

YES : Diagnosis is complete.
NO : Replace the valve body assembly. Then check the

symptom. If the symptom is not eliminated, go to Step
4.

STEP 3. Check the transaxle power train components.
Disassemble the transaxle and check the planetary carrier and
output shaft, etc. Repair or replace the damaged parts. Refer to
GROUP 23B, Transaxle

P.23B-10

, Planetary Gear

P.23B-58

,

Output Shaft

P.23B-62

, Differential

P.23B-64

. Then check the

symptom.

Q: Is the symptom eliminated?

YES : Diagnosis is complete.
NO : Go to Step 5.

AC001860 AB

VALVE
BODY
ASSEMBLY

AC004468AB

PLANETARY GEAR

OUTPUT SHAFT

DIFFERENTIAL

AUTOMATIC TRANSAXLE DIAGNOSIS

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AUTOMATIC TRANSAXLE

23A-224

STEP 4. Replace the oil pump.
(1) Remove the transaxle.
(2) Replace the oil pump (Oil pump cannot be repaired). Refer

to GROUP 23B, Transaxle

P.23B-10

. Then check the

symptom.

Q: Is the symptom eliminated?

YES : Diagnosis is complete.
NO : Go to Step 5.

STEP 5. Replace the PCM.

Q: Is the symptom eliminated?

YES : Diagnosis is complete.
NO : Start over at Step 1.

INSPECTION PROCEDURE 5: Engine Stalls when Moving Selector Lever from "N" to "D" or "N" to "R"

COMMENT
If the engine stalls when the selector lever is shifted
from "N" to "D" or "R" range while the engine is idling,
the cause is probably a malfunction of the engine
system, torque converter clutch solenoid valve, valve
body or torque converter (torque converter clutch
malfunction).

TROUBLESHOOTING HINTS (The most likely

causes for this case:)

•

Malfunction of the engine system

•

Malfunction of the torque converter clutch
solenoid

•

Malfunction of the valve body

•

Malfunction of the torque converter (Malfunction
of the torque converter clutch)

•

Malfunction of the PCM

DIAGNOSIS

STEP 1. Check the engine system.
Refer to GROUP 13A <2.4L Engine>, Diagnosis

−

Trouble

Symptom Chart

−

When the engine is hot, it stalls at idle

P.13A-

22

or GROUP 13B <3.0L Engine>, Diagnosis

−

Trouble

Symptom Chart

−

When the engine is hot, it stalls at idle

P.13B-

22

.

Q: Is the inspection result good?

YES : Go to Step 2.
NO : Repair or replace the engine components.

AC001858

AUTOMATIC TRANSAXLE DIAGNOSIS

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AUTOMATIC TRANSAXLE

23A-225

STEP 2. Replace the torque converter clutch solenoid
valve.
Replace the torque converter clutch solenoid valve. Refer to
GROUP 23B, Valve Body

P.23B-68

. Then check the symptom.

Q: Is the symptom eliminated?

YES : Diagnosis is complete.
NO : Go to Step 3.

STEP 3. Disassemble and clean the valve body.
Check the O-ring installation bolts for looseness and valve
body for damage. Repair or replace the faulty parts. Refer to
GROUP 23B, Valve Body

P.23B-68

.

Q: Is the repair possible and the symptom eliminated?

YES : Diagnosis is complete.
NO : Replace the valve body assembly. Then check the

symptom. If the symptom is not eliminated, go to Step
4.

STEP 4. Replace the torque converter assembly.
(1) Remove the transaxle.
(2) Replace the torque converter assembly. Refer to GROUP

23B, Transaxle

P.23B-10

. Then check the symptom.

Q: Is the symptom eliminated?

YES : Diagnosis is complete.
NO : Go to Step 5.

STEP 5. Replace the PCM.

Q: Is the symptom eliminated?

YES : Diagnosis is complete.
NO : Start over at Step 1.

INSPECTION PROCEDURE 6: Shift Shocks when Shifting from "N" to "D" and Long Delay

COMMENT
If abnormal shocks or delay of two seconds or more
occurs when the selector lever is shifted from "N" to
"D" range while the engine is idling, the cause is

probably abnormal underdrive clutch pressure or a
malfunction of the underdrive clutch, valve body or
throttle position sensor.

AC001866

AC001860 AB

VALVE
BODY
ASSEMBLY

AC001857

AUTOMATIC TRANSAXLE DIAGNOSIS

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AUTOMATIC TRANSAXLE

23A-226

TROUBLESHOOTING HINTS (The most likely

causes for this case:)

•

Abnormal underdrive clutch pressure

•

Malfunction of the underdrive solenoid valve

•

Malfunction of the underdrive clutch

•

Malfunction of the valve body

•

Malfunction of the throttle position sensor

•

Malfunction of the PCM

DIAGNOSIS

REQUIRED SPECIAL TOOL:
MB991502: Scan Tool (MUT-II)

STEP 1. Using scan tool MB991502, check actuator test
item 02: Underdrive Solenoid Valve.

CAUTION

To prevent damage to scan tool MB991502, always turn the
ignition switch to "LOCK" (OFF) position before
connecting or disconnecting scan tool MB991502.
(1) Connect scan tool MB991502 to the data link connector.
(2) Turn the ignition switch to "ON" position.
(3) Set scan tool MB991502 to actuator test mode for item 02:

Underdrive Solenoid Valve.

•

An operation sound should be heard from solenoid
valve when solenoid valve is operated.

(4) Turn the ignition switch to "LOCK" (OFF) position.

Q: Is the solenoid valve operating properly?

YES : Go to Step 2.
NO : Repair or replace the underdrive solenoid valve.

Refer to GROUP 23B, Valve Body

P.23B-68

. Then

confirm that the symptom is eliminated.

STEP 2. Check when shift shocks occur.

Q: When the shift shocks occur?

When engaging from N to D : Go to Step 3.
When the vehicle starts moving : Go to Step 6.

STEP 3. Check the hydraulic pressure (for underdrive
clutch).
Measure the hydraulic pressure for underdrive clutch when the
selector lever is shifted from "N" to "D" range. Check if the
hydraulic pressure is within the standard value. Refer to

P.23A-

23

, Hydraulic Pressure Test.

Q: Is the hydraulic pressure within the standard value?

YES : Go to Step 4.
NO : Go to Step 8.

AC003081AC

MB991502

DATA LINK
CONNECTOR