Code No.P1786: Torque Converter Clutch System (Stuck Off)


OPERATION



DIAGNOSIS CODE SET CONDITIONS



PROBABLE CAUSES



  • Malfunction of input shaft speed sensor
  • Damaged harness wires and connectors
  • Malfunction of the A/T-ECU
  • Malfunction of DCC 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 set, the input shaft speed sensor may be defective.

Q. Is diagnosis code P1766 set?
Refer to diagnosis code P1766: Input shaft speed sensor system .
Go to Step 2.

STEP 2. M.U.T.-III diagnosis code
If diagnosis code P1786 is set, the DCC solenoid valve may be defective.

Q. Is diagnosis code P1778 set?
Refer to diagnosis code P1778: DCC solenoid valve system .
Go to Step 3.

STEP 3. M.U.T.-III data list

  • Item 17: DCC 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 .

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.
The inspection is complete.