Inspection Procedure 18: Lock-up does not turn ON or OFF

COMMENTS ON TROUBLE SYMPTOM

If the lock-up is not performed or the lock-up is not cancelled, the cause is probably a malfunction of the engine system, lock-up solenoid system, stop lamp switch system, torque converter, or valve body.

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

<6B3>.

Refer to GROUP 13C - Troubleshooting

<4N1>.

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 (Refer to GROUP 54A - ETACS - Troubleshooting, Input Signal Procedures ).

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

Item 6: 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.