Mitsubishi Grandis. Manual - part 857

TROUBLESHOOTING <A/T>

AUTOMATIC TRANSMISSION (FF)

23A-95

YES : 

Go to Step 3.

NO : 

Refer to diagnosis code 22: Input shaft 
speed sensor system 

P.23A-27

.

STEP 3. MUT-III diagnosis code

Either of diagnosis codes 27 or 28 is set, inhibtor 
switch is defective.

Q: Are diagnosis codes 27 or 28 output?

YES <diagnosis code 27 is set> : 

Refer to 

diagnosis code 27: Inhibitor switch system 

P.23A-52

.

YES <diagnosis code 28 is set> : 

Refer to 

diagnosis code 28: Inhibitor switch system 

P.23A-59

.

NO : 

Go to Step 4.

STEP 4. MUT-III data list

Item 31: Low-reverse solenoid valve duty ratio (Refer 
to data list reference table 

P.23A-117

).

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Replace the engine-A/T-ECU.

STEP 5. Check when shift shock occurs.

Q: Does the shift shock occur when the vehicle starts 

moving?

YES : 

Go to Step 7.

NO : 

Go to Step 6.

STEP 6. Hydraulic pressure test

Measure the hydraulic pressure for reverse clutch 
and low-reverse clutch when the selector lever is 
shifted from N to R range.

OK: Refer to 

P.23A-133

.

Q: Is the check result normal?

YES : 

Go to Step 10.

NO : 

Go to Step 9.

STEP 7. Check when shift shock occurs.

Q: Does the shift shock always occur?

YES : 

Go to Step 9.

NO : 

Go to Step 8.

STEP 8. MUT-III data list

Item 11: Throttle position sensor (Refer to data list 
reference table 

P.23A-117

).

Q: Is the check result normal?

YES : 

Go to Step 9.

NO : 

Check the throttle position sensor system 
(Refer to GROUP 13, Troubleshooting 

P.13A-20

).

STEP 9. Valve body disassembly clean and 
assembly
(1) Check the bolts for looseness and the O-ring, 

solenoid valve, springs and valve body for 
damage.
Replace the valve body assembly if the damages 
are thought to be irreparable.

(2) Test drive the vehicle.
(3) Verify that the condition described by the 

customer exists.

Q: Does a malfunction take place again?

YES : 

Go to Step 10.

NO : 

The inspection is complete.

STEP 10. Reverse clutch and low-reverse brake 
check

Check the facing for seizure and the piston seal ring 
for damage and interference with the retainer.

Q: Is the check result normal?

YES : 

The inspection is complete.

NO : 

Repair or replace the reverse clutch and 
low-reverse brake.

INSPECTION PROCEDURE 9: Shift shock when shifting from N to D, N to R and long delay

COMMENTS ON TROUBLE SYMPTOM

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

POSSIBLE CAUSES

• Abnormal line pressure

• Malfunction of throttle position sensor

• Malfunction of oil pump

• Malfunction of valve body

• Malfunction of the engine-A/T-ECU

TROUBLESHOOTING <A/T>

AUTOMATIC TRANSMISSION (FF)

23A-96

DIAGNOSIS

STEP 1. Hydraulic pressure test

Measure the hydraulic pressure of each element 
when the selector lever is in L, 2nd or reverse.

OK: Refer to 

P.23A-133

.

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Go to Step 2.

STEP 2. Line pressure adjustment

(1) Adjust the line pressure (Refer to 

P.23A-138

).

(2) Test drive the vehicle.
(3) Verify that the condition described by the 

customer exists.

Q: Does a malfunction take place again?

YES : 

Go to Step 3.

NO : 

The inspection is complete.

STEP 3. Check when shift shock occurs.

Q: Does the shift shock occur when the vehicle starts 

moving?

YES : 

Go to Step 4.

NO : 

Replace the oil pump assembly (Oil pump 
cannot be repaired).

STEP 4. Check when shift shock occurs.

Q: Does the shift shock always occur?

YES : 

Go to Step 7.

NO : 

Go to Step 5.

STEP 5. MUT-III data list

Item 11: Throttle position sensor (Refer to data list 
reference table 

P.23A-117

).

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Check the throttle position sensor system 
(Refer to GROUP 13, Troubleshooting 

P.13A-20

).

STEP 6. Engine-A/T-ECU replacement
(1) Replace the engine-A/T-ECU.
(2) Test drive the vehicle.
(3) Verify that the condition described by the 

customer exists.

Q: Does a malfunction take place again?

YES : 

Go to Step 7.

NO : 

The inspection is complete.

STEP 7. Valve body disassembly clean and 
assembly

Check the bolts for looseness and the O-ring, 
solenoid valve s, springs and valve body for damage.

Q: Is the check result normal?

YES : 

The inspection is complete.

NO : 

Replace the valve body assembly if the 
damages are thought to be irreparable.

INSPECTION PROCEDURE 10: Shift shock and slipping

COMMENTS ON TROUBLE SYMPTOM

If shift shock when driving are 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.

POSSIBLE CAUSES

• Malfunction of each solenoid valve

• Abnormal line pressure

• Malfunction of valve body

• Malfunction of oil pump

• Malfunction of each brake or each clutch

• Malfunction of the engine-A/T-ECU

DIAGNOSIS

STEP 1. MUT-III actuator test

• Item 01: Low-reverse solenoid valve

• Item 02: Underdrive solenoid valve

• Item 03: Second solenoid valve

• Item 04: Overdrive solenoid valve

OK: Operating sound can be heard.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Replace the defective solenoid valve.

TROUBLESHOOTING <A/T>

AUTOMATIC TRANSMISSION (FF)

23A-97

STEP 2. MUT-III data list

• Item 63: Shift position (Refer to data list reference 

table 

P.23A-117

).

• Item 31, 32, 33, 34: Each solenoid valve duty 

ratio (Refer to data list reference table 

P.23A-117

).

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Replace the engine-A/T-ECU.

STEP 3. Hydraulic pressure test

Check all hydraulic pressures within the standard 
value.

OK: Refer to 

P.23A-133

.

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Go to Step 4.

STEP 4. Line pressure adjustment

(1) Adjust the line pressure (Refer to 

P.23A-138

).

(2) Test drive the vehicle.
(3) Verify that the condition described by the 

customer exists.

Q: Does a malfunction take place again?

YES : 

Go to Step 5.

NO : 

The inspection is complete.

STEP 5. Valve body disassembly clean and 
assembly
(1) Check the bolts for looseness and the O-ring, 

solenoid valves, springs and valve body for 
damage.
Replace the valve body assembly if the damages 
are thought to be irreparable.

(2) Test drive the vehicle.
(3) Verify that the condition described by the 

customer exists.

Q: Does a malfunction take place again?

YES : 

Check the oil pump for incorrect installation, 

damage and etc., and replace the oil pump 
assembly if necessary (The oil pump cannot 
be disassembled).

NO : 

The inspection is complete.

STEP 6. Each clutch and brake check

Check the facing for seizure and the piston seal ring 
for damage and interference with the retainer.

Q: Is the check result normal?

YES : 

The inspection is complete.

NO : 

Repair or replace each clutch and brake.

INSPECTION PROCEDURE 11: Does not shift properly (all points)

COMMENTS ON TROUBLE SYMPTOM

If all shift points are early or late while driving, the 
cause is probably a malfunction of the output shaft 
speed sensor, throttle position sensor, or 
engine-A/T-ECU.

POSSIBLE CAUSES

• Malfunction of output shaft speed sensor

• Malfunction of throttle position sensor

• Malfunction of the engine-A/T-ECU

DIAGNOSIS

STEP 1. MUT-III data list

Item 0002: Output shaft speed sensor (Refer to data 
list reference table 

P.23A-117

).

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Refer to diagnosis code 23: Output shaft 
speed sensor system 

P.23A-37

.

STEP 2. MUT-III data list

Item 11: Throttle position sensor (Refer to data list 
reference table 

P.23A-117

).

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Check the throttle position sensor system 
(Refer to GROUP 13, Troubleshooting 

P.13A-20

).

STEP 3. MUT-III actuator test
(1) Item 14: INVECS-II cancel command
(2) Test drive the vehicle (Refer to Road Test, 

Inspection procedure 8 

P.23A-8

).

(3) Check that the gear shifting corresponds to the 

standard shift line of the shift pattern diagram.

Q: Is the check result normal?

YES : 

The inspection is complete.

NO : 

Replace the engine-A/T-ECU.

TROUBLESHOOTING <A/T>

AUTOMATIC TRANSMISSION (FF)

23A-98

INSPECTION PROCEDURE 12: Does not shift properly (some point)

COMMENTS ON TROUBLE SYMPTOM

If some of the shift points are early or late when 
driving, the cause is probably a malfunction of valve 
body, or it is due to the characteristics of the 
INVECS-II system but is not an abnormality.

POSSIBLE CAUSES

• Malfunction of valve body

• Malfunction of the engine-A/T-ECU

DIAGNOSIS

STEP 1. Check when the shift points early or late.

Q: Are the shift points early or late only when A/T fluid 

is 

−20°C or less, or 125°C or more?

YES : 

The symptom is due to characteristics of the 

INVECS-II system, but is not abnormal.

NO : 

Go to Step 2.

STEP 2. MUT-III actuator test
(1) Item 14: INVECS-II cancel command
(2) Test drive the vehicle (Refer to Road Test, 

Inspection procedure 8 

P.23A-8

).

(3) Check that the gear shifting corresponds to the 

standard shift line of the shift pattern diagram.

Q: Is the check result normal?

YES : 

The inspection is complete.

NO : 

Replace the engine-A/T-ECU.

INSPECTION PROCEDURE 13: Does not shift (no diagnosis code)

COMMENTS ON TROUBLE SYMPTOM

The gear shifting does not occur while driving. If no 
diagnosis codes are set, the cause is probably a 
malfunction of the shift switch assembly or 
engine-A/T-ECU .

POSSIBLE CAUSES

• Malfunction of Shift switch assembly

• Malfunction of the engine-A/T-ECU

DIAGNOSIS

STEP 1. MUT-III data list
Item 54: A/T control relay (Refer to Data List 
Reference Table 

P.23A-117

).

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Replace the engine-A/T-ECU.

STEP 2. MUT-III data list
Item 67: Select switch (Refer to Data List Reference 
Table 

P.23A-117

).

Q: Is the check result normal?

YES : 

Replace the engine-A/T-ECU.

NO : 

INSPECTION PROCEDURE 16: Shift 
switch assembly system check (Refer to 

P.23A-100

).

INSPECTION PROCEDURE 14: Poor acceleration

COMMENTS ON TROUBLE SYMPTOM

If acceleration is poor when downshifting occurs 
while driving, the cause is probably a malfunction of 
the engine system.

POSSIBLE CAUSES

• Malfunction of engine system

• Malfunction of the engine-A/T-ECU

DIAGNOSIS

STEP 1. Engine system check

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the engine system.