Mitsubishi L200. Manual - part 296

TROUBLESHOOTING

AUTOMATIC TRANSMISSION

23A-91

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list
Item 06: Output shaft speed sensor (Refer to data list 
reference table 

P.23A-103

).

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Refer to diagnosis code P1767: Output 
shaft speed sensor system 

P.23A-41

.

STEP 2. M.U.T.-III data list
Item 35: Accelerator pedal position sensor (Refer to 
data list reference table 

P.23A-103

).

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

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

STEP 3. M.U.T.-III actuator test
(1) Test drive the vehicle (Refer to Road Test, 

Inspection procedure 8 

P.23A-17

).

(2) 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 A/T-ECU.

Inspection Procedure 12: Does not Shift Properly (some Point)

COMMENTS ON TROUBLE SYMPTOM
If some of the shift points are early or late when driv-
ing, the cause is probably a malfunction of valve 
body.

PROBABLE CAUSES

• Malfunction of the A/T-ECU

DIAGNOSIS PROCEDURE

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 : 

Is not abnormal.

NO : 

Go to Step 2.

STEP 2. M.U.T.-III actuator test
(1) Test drive the vehicle (Refer to Road Test, 

Inspection procedure 8 

P.23A-17

).

(2) 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 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 mal-
function of the shift switch assembly or A/T-ECU .

PROBABLE CAUSES

• Malfunction of Shift switch assembly

• Malfunction of the A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list
Item 08: A/T control relay (Refer to Data List Refer-
ence Table 

P.23A-103

).

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Replace the A/T-ECU.

STEP 2. M.U.T.-III data list
Item 34: Inhibitor switch (Refer to Data List Refer-
ence Table 

P.23A-103

).

Q: Is the check result normal?

YES : 

Replace the A/T-ECU.

NO : 

Refer to diagnosis code P1770 (P0705): 
Inhibitor switch system 

P.23A-46

 <4A/T>, 

P.23A-49

 <5A/T> and Refer to diagnosis 

code P1771 (P0705): Inhibitor switch 
system 

P.23A-51

 <4A/T>, 

P.23A-52

  <5A/

T>.

TROUBLESHOOTING

AUTOMATIC TRANSMISSION

23A-92

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.

PROBABLE CAUSES

• Malfunction of engine system

• Malfunction of the A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Engine system check

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the engine system.

STEP 2. A/T-ECU replacement
(1) Replace the 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 1.

NO : 

The inspection is complete.

Inspection Procedure 15: Vibration

COMMENTS ON TROUBLE SYMPTOM
If vibration occurs when driving at constant speed or 
when acceleration in high range, the cause is proba-
bly an abnormal torque converter pressure, or a mal-
function of the engine system, damper clutch 
solenoid valve, valve body or torque converter.

PROBABLE CAUSES

• Malfunction of damper clutch solenoid valve

• Malfunction of engine system

• Abnormal torque converter pressure

• Malfunction of valve body

• Malfunction of torque converter

• Malfunction of the A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check when the vibration occurs.

Q: Does the vibration occur when the damper clutch 

is operating?
YES : 

Go to Step 3.

NO : 

Go to Step 2.

STEP 2. Engine system check

Q: Is the check result normal?

YES : 

The inspection is complete.

NO : 

Repair the engine system.

STEP 3. A/T-ECU replacement
(1) Replace the 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 4.

NO : 

The inspection is complete.

STEP 4. Torque converter check
Check for damaged drive plate, incorrect installation 
in the input shaft (inserted at an angle), damaged 
splines or damper clutch sealing.

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

If repair is possible, repair the damaged 
part. If repair is not possible because the 
splines on the drive plate or torque 
converter are damaged, replace it.

STEP 5. Valve body disassembly clean and 
assembly
Check the bolts for looseness and the O-ring, sole-
noid valve 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.

TROUBLESHOOTING

AUTOMATIC TRANSMISSION

23A-93

Inspection Procedure 16: Overdrive switch system <4A/T>

AC903911

IGNITION 
SWITCH (IG1)

A/T-ECU

OVERDRIVE 
SWITCH

Wire colour code
B : Black 
LG : Light green
G : Green
L: Blue 
W : White
Y: Yellow
SB : Sky blue
BR : Brown 
O : Orange
GR : Grey  
R : Red 
P : Pink  
V : Violet
PU: Purple

Overdrive Switch System Circuit

AC510057

Harness side

A/T-ECU

C-20

AC

Connector: C-20

A/T-ECU

<RHD>

<LHD>

AC509930AG

Connector: C-34 <RHD>

C-34

Harness side

AC509613AG

Connector: C-52 <LHD>

C-52

Harness side

AC509611CX

Connector: C-129 <LHD>

Harness side

C-129

AC509932DE

Connector: C-129 <RHD>

Harness side

C-129

AC509934

Connectors: C-207, C-208 <LHD>

Junction block (Front view)

C-208

CX

Harness side

C-207

AC509936

Connectors: C-207, C-208 <RHD>

Harness side

C-208

C-207

BZ

Junction block 
(Front view)

TROUBLESHOOTING

AUTOMATIC TRANSMISSION

23A-94

OPERATION
During driving with 4th gear, when the overdrive 
switch is turned ON, A/T-ECU performs a downshift 
control to 3rd gear.

COMMENTS ON TROUBLE SYMPTOM
If downshifting does not occur when overdrive switch 
is turned on while driving in 4th gear, or upshifting 
does not occur when overdrive switch is turned off 
while driving in 3rd gear, the cause is probably a 
problem in the overdrive switch system.

PROBABLE CAUSES

• Malfunction of the overdrive switch

• Damaged harness wires and connectors

• Malfunction of the A/T-ECU