The A/T-ECU engages and disengages the damper clutch (incorporated in the torque
converter) by operating the DCC solenoid valve in response to driving conditions.
DIAGNOSIS CODE SET CONDITIONS
If the damper clutch solenoid valve drive duty ratio is 100%
for a continuous
period of 4 seconds or more when the damper clutch starts operating, diagnosis code No.P1786
is output.
PROBABLE CAUSES
Malfunction of input shaft speed sensor
Damaged harness wires and connectors
Malfunction of the A/T-ECU
Malfunction of damper clutch solenoid valve
Malfunction of valve body assembly
Malfunction of torque converter
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III diagnosis code
If diagnosis code P1786 is output, the input shaft speed sensor may be defective.
Q.
Is diagnosis code P1766 (P0715) set?
Refer to diagnosis code P1766 (P0715): Input shaft speed sensor system .
Go to Step 2.
STEP 2. M.U.T.-III diagnosis code
If diagnosis code P1786 is output, the damper clutch solenoid valve may be defective.
Q.
Is diagnosis code P1778 (P0740) set?
Refer to diagnosis code P1778 (P0740): Damper clutch solenoid valve system .
Go to Step 3.
STEP 3. M.U.T.-III data list
Item 17: Damper clutch solenoid valve duty ratio (Refer to data list reference
table ).
Item 10: Damper clutch slip amount (Refer to data list reference table ).
Q.
Is the check result normal?
Go to Step 6.
Go to Step 4.
STEP 4. Hydraulic pressure test
Measure the torque converter hydraulic pressure. (Refer to .)
OK: Refer to Hydraulic Pressure Test .
Q.
Is the check result normal?
Go to Step 6.
Go to Step 5.
STEP 5. Adjust the line pressure and recheck the diagnosis code.
(1)Adjust the line pressure (Refer to ).
(2)Test drive the vehicle.
(3)Check the diagnosis code.
Q.
Is the diagnosis code set?
Go to Step 7.
The inspection is complete.
STEP 6. Replace the A/T-ECU and then recheck the diagnosis
code.
(1)Replace the A/T-ECU.
(2)Test drive the vehicle.
(3)Check the diagnosis code.
Q.
Is the diagnosis code set?
Go to Step 7.
The inspection is complete.
STEP 7. Disassemble, clean and assemble the valve body and recheck
the diagnosis code.
(1)Check the mounting bolts for looseness, and the O-ring, solenoid valve and valve
body for damage. Replace the valve body assembly if the damages are thought to be irreparable.
(2)Test drive the vehicle.
(3)Check the diagnosis code.
Q.
Is the diagnosis code set?
Check the torque converter and replace it if necessary.
Refer to diagnosis code P1766 (P0715): Input shaft speed sensor system 
.
Go to Step 2.