Mitsubishi 380. Manual - part 424

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-236

STEP 5. Disassemble and clean the valve body.
Check the installation bolts for looseness and the O-ring,
valves and valve body for damage. Repair or replace the faulty
parts. Refer to GROUP 23B, Valve Body

P.23B-62

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 : Start over at Step 1.

INSPECTION PROCEDURE 9: Shift Shock and Slipping

COMMENT

If shift shock when driving is due to upshifting or
downshifting and the transmission speed become
higher than the engine speed, the cause is probably
abnormal line pressure or a malfunction of a solenoid
valve, oil pump, valve body or of a brake or clutch.

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

• Abnormal line pressure

• Malfunction of each solenoid valve

• Malfunction of the oil pump

• Malfunction of the valve body

• Malfunction of each brake or each clutch

• Malfunction of the A/T-ECU system

Circuit drawings

• Refer to circuit diagrams GROUP-

• Refer to configuration diagrams GROUP-

• Refer to component locations GROUP-

DIAGNOSIS

Required Special Tool:

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

• MB991824: V.C.I.

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A

VALVE BODY
ASSEMBLY

10DB117A

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-237

STEP 1. Using diagnostic tool MB991958, check actuator
test.

CAUTION

To prevent damage to diagnostic tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting diagnostic tool
MB991958.
(1) Connect diagnostic tool MB991958 to the data link

connector.

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

following items.

a. Item 01: Low-reverse solenoid valve
b. Item 02: Underdrive solenoid valve

c. Item 03: Second solenoid valve

d. Item 04: Overdrive solenoid valve
e. Item 05: Reduction solenoid valve

• An audible clicking or buzzing should be heard when

the solenoid valves are energized.

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

Q: Are the solenoid valves operating properly?

YES : Go to Step 2.
NO : Repair or replace the solenoid valves. Refer to

GROUP 23B, Valve Body

P.23B-62

. Then confirm

that the symptom is eliminated.

STEP 2. Check the hydraulic pressure.
(1) Measure the hydraulic pressure of each element. Check if

each hydraulic pressure is within the standard value. Refer
to

P.23A-26

, Hydraulic Pressure Test.

(2) If some elements pressure are within the standard value

and some are not, recheck the symptom.

Q: Are all hydraulic pressures within the standard value?

YES : Go to Step 6.
NO : Go to Step 3.

STEP 3. Adjust the line pressure.
Adjust the line pressure. Refer to

P.23A-33

, Line Pressure

Adjustment. Then check the symptom.

Q: Is the symptom eliminated?

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

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-238

STEP 4. 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-62

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 5.

STEP 5. Check the oil pump.
(1) Remove the transmission.
(2) Check the oil pump (incorrect installation, damage and etc.)

and replace the oil pump assembly if necessary (The oil
pump cannot be disassembled).Refer to GROUP 23B,
Transmission

P.23B-13

. Confirm that the malfunction

symptom is eliminated.

Q: Is the symptom eliminated?

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

STEP 6. Check each brake and clutch.
(1) Remove the transmission.
(2) Check the facing 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-13

, Underdrive Clutch and Input Shaft

P.23B-46

Reverse and Overdrive Clutch

P.23B-48

. Then Retest the

system.

Q: Is the symptom eliminated?

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

VALVE BODY
ASSEMBLY

10DB117A

AC001865

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-239

23A

INSPECTION PROCEDURE 10: Early or Late Shifting in All Gears

COMMENT

If all shift points are early or late while driving, the
cause is probably a malfunction of the output shaft
speed sensor, TP sensor or a solenoid valve.

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

• Malfunction of the output shaft speed sensor

• Malfunction of the TP sensor

• Malfunction of each solenoid valve

• Abnormal line pressure

• Malfunction of the valve body

• Malfunction of the A/T-ECU system

Circuit drawings

• Refer to circuit diagrams GROUP-

• Refer to configuration diagrams GROUP-

• Refer to component locations GROUP-

DIAGNOSIS

Required Special Tool:

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

• MB991824: V.C.I.

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A

STEP 1. Using diagnostic tool MB991958, check A/T data
list item 6: Output Shaft Speed Sensor.

CAUTION

connector.

(2) Start the engine.
(3) Set diagnostic tool MB991958 to the data reading mode.

• Item 6: Output Shaft Speed Sensor.

• When driving at constant speed of 50km/h, the dis-

play should be "1,100 - 1,400 r/min" (Gear range:
3rd gear).

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

Q: Is the sensor operating properly?

YES : Go to Step 2.
NO : Refer to

P.23A-72

, DTC (P0720): Output shaft speed

sensor system.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

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