Inspection Procedure 15: Lock-up does not turn ON or OFF


COMMENTS ON TROUBLE SYMPTOM



PROBABLE CAUSES



  • Malfunction of engine system
  • Malfunction of stop lamp switch system
  • Malfunction of torque converter
  • Malfunction of valve body (lock-up solenoid)
  • Malfunction of the A/T-ECU
  • Malfunction of A/T fluid temperature sensor 1 system
  • A/T internal error (oil pump, clutches, brakes, etc.)

DIAGNOSIS PROCEDURE

STEP 1. Engine system check
Refer to GROUP 13B - Troubleshooting .
note It is highly possible that a malfunction is present to the accelerator pedal position sensor system or coolant temperature sensor system.

Q. Is the check result normal?
Go to Step 2.
Repair the engine system.

STEP 2. Stop lamp switch system check
The stop lamps should illuminate when the brake pedal is depressed, and extinguish when released.

Q. Is the check result normal?
Go to Step 3.
Refer to stop lamp switch system ().

STEP 3. M.U.T.-III data list
Item 7: A/T fluid temperature sensor 1 (Refer to data list reference table ).

Q. Is the check result normal?
Go to Step 4.
Repair the A/T fluid temperature sensor 1 system.

STEP 4. Torque converter stall test
Carry out the torque converter stall test (Refer to ), and replace the torque converter if the result is out of the standard value. Then, check the trouble symptom again.

Q. Is the trouble symptom reproduced?
Go to Step 5.
This diagnosis is complete.

STEP 5. Retest the system
If the trouble symptom is not solved, replace the valve body. Then, check the trouble symptom again.

Q. Is the trouble symptom reproduced?
Go to Step 6.
This diagnosis is complete.

STEP 6. 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. Is the trouble symptom reproduced?
After checking the oil pump for damage, check each clutch and brake for any damage, and replace if necessary.
This diagnosis is complete.