Inspection Procedure 5: Slip at backward driving

COMMENTS ON TROUBLE SYMPTOM

If a slip occurs during backward driving, the cause is probably an abnormal line pressure or a malfunction of the line pressure control solenoid system, input shaft speed sensor system, torque converter, valve body, or oil pump.

PROBABLE CAUSES

Insufficient A/T fluid amount, immixing of water or unspecified A/T fluid
Malfunction of input shaft speed sensor system
Malfunction of torque converter
Malfunction of valve body (line pressure control solenoid)
Malfunction of the A/T-ECU
A/T internal error (oil pump, clutch C3, brake B1/B4, one-way clutch F1, etc.)

DIAGNOSIS PROCEDURE

STEP 1. A/T fluid check

Check the A/T fluid for amount and condition (not severely contaminated), and fill or replace the A/T fluid if necessary. Then, check the trouble symptom again.

Q. Is the trouble symptom reproduced?

	Go to Step 2.

	This diagnosis is complete.

STEP 2. M.U.T.-III data list

Item 4: Input shaft speed sensor (Refer to data list reference table

Q. Is the check result normal?

	Go to Step 3.

	Repair the input shaft speed sensor system.

STEP 3. Hydraulic pressure test

Measure the line pressure (Refer to

note

If a slip occurs during backward driving, the line pressure may be lower than the standard value.

OK: Refer to .

Q. Is the check result normal?

	Go to Step 4.

	Go to Step 5.

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 6.

	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. (It is highly possible that the clutch C3, brake B1/B4, and one-way clutch F1 that engage in reverse gear are damaged.)

	This diagnosis is complete.