Mitsubishi Montero (2004+). Manual - part 933

AUTOMATIC TRANSMISSION DIAGNOSIS

TSB Revision

AUTOMATIC TRANSMISSION

23A-307

STEP 3. Check the underdrive clutch system.
(1) Remove the valve body cover and valve body. Refer to 

P.23A-563

, Transmission and Transfer Assembly and refer 

to GROUP 23B, Transmission 

P.23B-14

.

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

clutch oil orifice of the transmission case, and check if the 
underdrive clutch piston moves and air pressure is 
maintained in that condition.

Q: Is the air pressure maintained?

YES : Go to Step 4.
NO :  Go to Step 5.

STEP 4. 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-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 5. Check the underdrive clutch.
(1) Remove the transmission assembly.
(2) Check the facing for seizure and the piston seal ring for 

damage and interference with the retainer. Repair or 
replace the faulty parts. Refer to GROUP 23B, Underdrive 
Clutch and Input Shaft 

P.23B-59

. 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.

ACX02249AB

UNDERDRIVE
CLUTCH OIL
ORIFICE

ACX02161AD

VALVE BODY ASSEMBLY

AC204883 AB

AUTOMATIC TRANSMISSION DIAGNOSIS

TSB Revision

AUTOMATIC TRANSMISSION

23A-308

INSPECTION PROCEDURE 3: Does not Move Backward

.

COMMENT
If the vehicle does not move backward when the 
selector lever is shifted from "N" to "R" range while 
the engine is idling, the cause is probably abnormal 
pressure or a malfunction of the reverse clutch, 
low-reverse brake, or valve body.

.

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

• Abnormal reverse clutch pressure

• Abnormal low-reverse brake pressure

• Malfunction of the low-reverse solenoid valve

• Malfunction of the reverse clutch

• Malfunction of the low-reverse brake

• 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

STEP 1. Using scan tool MB991958, check actuator test 
item 01: Low-Reverse 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 01: Low-Reverse Solenoid Valve.

• An audible clicking or buzzing should be heard when 

the low-reverse solenoid valve is energized.

(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 low-reverse solenoid valve. 

Refer to GROUP 23B, Valve Body 

P.23B-63

. Then 

confirm that the symptom is eliminated.

AC307591 AC

MB991911

MB991824

MB991827

AC307591

DATA LINK

CONNECTOR

AUTOMATIC TRANSMISSION DIAGNOSIS

TSB Revision

AUTOMATIC TRANSMISSION

23A-309

STEP 2. Check the hydraulic pressure (for reverse clutch).
Measure the hydraulic pressure for reverse clutch when the 
selector lever is at the "R" range, and check if the hydraulic 
pressure is within the standard value. Refer to 

P.23A-26

, 

Hydraulic Pressure Test.
Q: Is the hydraulic pressure within the standard value?

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

STEP 3. Check the hydraulic pressure (for low-reverse 
brake).
Measure the hydraulic pressure for low-reverse brake when the 
selector lever is at the "R" range, and check if the hydraulic 
pressure is within the standard value. Refer to 

P.23A-26

, 

Hydraulic Pressure Test.
Q: Is the hydraulic pressure within the standard value?

YES : Go to Step 4.
NO :  Go to Step 5.

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

P.23A-563

, Transmission and Transfer Assembly and refer 

to GROUP 23B, Transmission 

P.23B-14

.

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

clutch oil orifice of the Transmission case. Then check if the 
reverse clutch piston moves and air pressures are 
maintained in that condition. Repeat for the low-reverse 
brake.

Q: Are the reverse clutch, low-reverse brake or both air 

pressures maintained?
YES : Go to Step 5.
NO :  Go to Step 6.

STEP 5. 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-63

.

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

YES : The procedure is complete.
NO :  Go to Step 7.

ACX02249AC

REVERSE
CLUTCH OIL
ORIFICE

LOW-REVERSE
BRAKE OIL
ORIFICE

ACX02161AD

VALVE BODY ASSEMBLY

AUTOMATIC TRANSMISSION DIAGNOSIS

TSB Revision

AUTOMATIC TRANSMISSION

23A-310

STEP 6. Check the reverse clutch, low-reverse brake or 
both. Remove the Transmission.
Check the facing for seizure and the piston seal ring for dam-
age and interference with the retainer. Repair or replace the 
faulty parts. Refer to GROUP 23B, Transmission 

P.23B-14

, 

Reverse and Overdrive Clutch 

P.23B-50

. Then check the 

symptom.
Q: Is the symptom eliminated?

YES : The procedure is complete.
NO :  Go to Step 7.

STEP 7. Replace the PCM.
Q: Is the symptom eliminated?

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

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 
powertrain, transmission 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 transmission oil pump

• Malfunction of the valve body

• Low transmission fluid level

• Malfunction of the PCM

DIAGNOSIS

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

P.23A-26

, 

Hydraulic Pressure Test. If some elements pressure are within 
the standard value and some are not, recheck the symptom.
Q: Are all pressures within the standard value?

YES : Check transmission fluid level and condition. If not 

OK, repair or replace as necessary, then retest the 
system. If OK, go to Step 3.

NO :  Go to Step 2.

AC204883

REVERSE
CLUTCH

LOW-REVERSE
BRAKE

AC