Mitsubishi 380. Manual - part 423

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-232

INSPECTION PROCEDURE 7: Shift Shock when Shifting from "N" to "R" and Long Delay

COMMENT

If abnormal shock or delay of two seconds or more
occurs when the selector lever is shifted from "N" to
"R" range while the engine is idling, the cause is
probably abnormal reverse clutch pressure or
low-reverse brake pressure, or a malfunction of the
reverse clutch, low-reverse brake, valve body or TP
sensor.

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

• 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 TP sensor

• 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 actuator
test item 01: Low-Reverse Solenoid Valve.

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.

• 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-62

. Then

confirm that the symptom is eliminated.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-233

STEP 2. Check when shift shock occurs.

Q: When does the shift shock occur?

When engaging from "N" to "R" : Go to Step 3.
When the vehicle starts moving : Go to Step 7.

STEP 3. Check the hydraulic pressure (for reverse clutch).
Measure the hydraulic pressure for reverse clutch when the
selector lever is at the "R" range. Check if the hydraulic pres-
sure 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 9.

STEP 4. 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. Check if the hydraulic pres-
sure 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 5.
NO : Go to Step 9.

STEP 5. Check the reverse clutch system and low-reverse
brake system.
(1) Remove the valve body cover and valve body. Refer to

P.23A-304

<F5A5A>, Transmission Assembly and GROUP

23B, Transmission

P.23B-13

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

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

Q: Are both air pressures maintained?

YES : Go to Step 6.
NO : Go to Step 9.

STEP 6. Check the reverse clutch and low-reverse brake.
(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,
Transmission

P.23B-13

, 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.

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-234

STEP 7. Check shift shock.

Q: Does shift shock occur sometimes?

YES : Go to Step 8.
NO : Go to Step 9.

STEP 8. Using diagnostic tool MB991958, check MPI data
list item 13: TP Sensor (main).

CAUTION

connector.

(2) Turn the ignition switch to the "ON" position.
(3) Set diagnostic tool MB991958 to the data reading mode.

• Item 13: TP Sensor (main).

• With the throttle valve in idle position, voltage should

measure between 1100 and 1200 mV.

• With the throttle valve in full-open position, voltage

should measure 4,000 mV or more.

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

Q: Is the measured voltage between 1100 and 1200 mV at

idle, and 4,000 mV or more at the full-open position?
YES : Go to Step 9.
NO : Check the TP sensor. Refer to GROUP13A <3.8L

Engine>, Diagnostic Trouble Code Procedures

13A-17

, DTCs P0122, P0123: TP Sensor System.

Then check the symptom.

STEP 9. 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 : Start over at Step 1.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

VALVE BODY
ASSEMBLY

10DB117A

AUTOMATIC TRANSMISSION DIAGNOSIS

AUTOMATIC TRANSMISSION

23A-235

INSPECTION PROCEDURE 8: Shift Shock when Shifting from "N" to "D," "N" to "R" and Long Delay

COMMENT

If abnormal shock or delay of two seconds or more
occurs when the selector lever is moved from "N" to
"D" range or from "N" to "R" range while the engine is
idling, the cause is probably abnormal line pressure
or a malfunction of the oil pump or valve body.

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

• Abnormal line pressure

• Malfunction of the oil pump

• 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

STEP 1. Check the hydraulic pressure.
(1) 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.

(2) If some elements pressures 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 3.
NO : Go to Step 2.

STEP 2. Adjust line pressure.
Adjust line pressure. Refer to

P.23A-33

, Line Pressure Adjust-

ment. Then check the symptom.

Q: Is the symptom eliminated?

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

STEP 3. Check when shift shock occurs.

Q: When does the shift shock occur?

When engaging from "N" to "D" and "N" to "R" : Go to

Step 4.

When the vehicle starts moving : Go to Step 5.

STEP 4. 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.

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