Mitsubishi Montero (2004+). Manual - part 940

AUTOMATIC TRANSMISSION DIAGNOSIS

TSB Revision

AUTOMATIC TRANSMISSION

23A-335

INSPECTION PROCEDURE 13: Poor Acceleration

.

COMMENT
If acceleration is poor when downshifting occurs 
while driving, a malfunction of the engine system or a 
brake or clutch may exist.

.

TROUBLESHOOTING HINTS (THE MOST LIKELY 
CAUSES FOR THIS CASE:)

• Malfunction of the engine system

• Malfunction of the clutch system and brake sys-

tem

• Malfunction of the PCM

DIAGNOSIS

STEP 1. Check the engine system.
Refer to GROUP 13A, Diagnosis 

− Symptom Chart − Poor 

Acceleration 

P.13A-885

.

Q: Is the inspection result good?

YES : Go to Step 2.
NO :  Repair or replace the engine component(s).

STEP 2. Check each brake and clutch.
Perform the torque converter stall test. Refer to 

P.23A-25

, 

Torque Converter Stall Test. Then retest the system.
Q: Is the symptom eliminated?

YES : The procedure is complete.
NO :  Go to Step 3.

STEP 3. Perform the hydraulic pressure test.
Perform the hydraulic pressure test. Refer to 

P.23A-26

, 

Hydraulic Pressure Test. Then retest the system.
Q: Is the symptom eliminated?

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

STEP 4. Check each brake system and clutch system.
(1) Remove the valve body cover and valve body. Refer to 

GROUP 23B, Transmission 

P.23B-14

.

(2) Blow 108 kPa (15 psi) compressed air into the each brake 

oil orifice and clutch oil orifice of the transmission case, and 
check if each brake and each clutch piston move and air 
pressure is maintained.

Q: Is the air pressure maintained?

YES : The procedure is complete.
NO :  Go to Step 5.

ACX02249 AF

OVERDRIVE CLUTCH
OIL ORIFICE

REVERSE
CLUTCH
OIL ORIFICE

SECOND
BRAKE OIL
ORIFICE

LOW-REVERSE
BRAKE OIL ORIFICE

UNDERDRIVE
CLUTCH OIL
ORIFICE

DIRECT
CLUTCH
OIL ORIFICE

REDUCTION
BRAKE OIL
ORIFICE

AUTOMATIC TRANSMISSION DIAGNOSIS

TSB Revision

AUTOMATIC TRANSMISSION

23A-336

STEP 5. Check each brake system and clutch system.
(1) Remove the transmission.
(2) Check the facings for seizure and piston seal ring for 

damage and interference with retainer. Repair or replace 
the faulty parts. Refer to GROUP 23B, Transmission 

P.23B-14

, Underdrive Clutch 

P.23B-59

, Reverse and 

Overdrive Clutches 

P.23B-50

, Direct Clutch 

P.23B-71

. 

Then check for the symptom.

Q: Is the symptom eliminated?

YES : The procedure is complete.
NO :  Go to Step 6.

STEP 6. Replace the PCM.
Q: Is the symptom eliminated?

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

INSPECTION PROCEDURE 14: Vibration

.

COMMENT
If vibration occurs when driving at constant speed or 
when accelerating in 4th gear, abnormal torque con-
verter clutch pressure a malfunction of the engine 
system, torque converter clutch solenoid, torque con-
verter or valve body may exist.

.

TROUBLESHOOTING HINTS (THE MOST LIKELY 
CAUSES FOR THIS CASE:)

• Abnormal torque converter clutch pressure

• Malfunction of the engine system

• Malfunction of the torque converter clutch sole-

noid

• Malfunction of the torque converter

• Malfunction of the valve body

• Malfunction of the PCM

DIAGNOSIS

Required Special Tool:

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

• MB991824: V.C.I.

• MB991827: MUT-III USB Cable

• MB991911: MUT-III Main Harness B

AC204883 AH

OVERDRIVE
CLUTCH

REDUCTION
BRAKE

REVERSE
CLUTCH

SECOND
BRAKE

LOW-REVERSE
BRAKE

UNDERDRIVE
CLUTCH

DIRECT
CLUTCH

AUTOMATIC TRANSMISSION DIAGNOSIS

TSB Revision

AUTOMATIC TRANSMISSION

23A-337

STEP 1. Using scan tool MB991958, check actuator test 
item 06: Torque Converter Clutch Solenoid Valve.

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) Turn the ignition switch to the "ON" position.
(3) Set scan tool MB991958 to the actuator test mode.

• Item 06: Torque Converter Clutch Solenoid Valve.

• An audible clicking or buzzing should be heard when 

the torque converter clutch solenoid valve is ener-
gized.

(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the solenoid valve operating properly?

YES : Go to Step 2.
NO :  Repair or replace the torque converter clutch solenoid 

valve. Refer to GROUP 23B, Valve Body 

P.23B-63

. 

Then confirm that the symptom is eliminated.

STEP 2. Check the vibration.
Q: Does the vibration occur when the transmission fluid 

temperature sensor connector has been disconnected?
YES : Check the engine system. Refer to GROUP 13A, 

Diagnosis 

− Symptom Chart − Driving 

P.13A-30

. If the 

inspection result is not good, diagnose, repair, and/or 
replace the engine component(s).

NO :  Go to Step 3.

STEP 3. Check the torque converter hydraulic pressure.
Measure the torque converter hydraulic pressure. Then check if 
the torque converter hydraulic pressure is within the standard 
value. Refer to 

P.23A-26

, Hydraulic Pressure Test.

Q: Is the torque converter hydraulic pressure within the 

standard value?
YES : Go to Step 4.
NO :  Go to Step 5.

AC307591 AC

MB991911

MB991824

MB991827

AC307591

DATA LINK

CONNECTOR

AUTOMATIC TRANSMISSION DIAGNOSIS

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AUTOMATIC TRANSMISSION

23A-338

STEP 4. Replace the torque converter assembly.
(1) Remove the transmission.
(2) Replace the torque converter assembly. Then check the 

symptom.

Q: Is the symptom eliminated?

YES : The procedure is complete.
NO :  Go to Step 6.

STEP 5. 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-63

.

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 6.

STEP 6. Replace the PCM.
Q: Is the symptom eliminated?

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

AC204883 AE

ACX02161AD

VALVE BODY ASSEMBLY