Inspection Procedure 14: HSA (Hill Start Assist) does not work.

caution

If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - Troubleshooting ).
Whenever ECU is replaced, ensure that the CAN bus lines are normal.
When the hydraulic unit assembly (integrated with ASTC-ECU) is replaced, always carry out the calibration of the steering wheel sensor and the G sensor (Refer to ).

COMMENTS ON TROUBLE SYMPTOM

The slope gradient may be low.
The vehicle is not completely stationary.
A failure may have occurred in the calibration of the G sensor.
A defective parking brake may cause the HSA not to function.
A problem (noise interference) may have occurred in the CAN bus line, resulting in an improper communication with ASTC-ECU or each ECU.

note

The HSA does not work even when the wheel speed sensor output pulse (vehicle moved) while the vehicle is parked.
The HSA is affected by the loading conditions and vehicle posture at the occurrence of phenomenon. When checking the HSA operation in actual driving, carry out the check on the vehicle with one occupant (driver) only.

PROBABLE CAUSES

Calibration failure of the G sensor
Malfunction of parking brake
Malfunction of combination meter
Malfunction of wheel speed sensor
Malfunction of A/T-ECU
Malfunction of hydraulic unit assembly (integrated with ASTC-ECU)
Wiring harness or connector failure of CAN bus line
Damaged wiring harness and connectors

DIAGNOSIS PROCEDURE

STEP 1. HSA function check

Check if the HSA works with one occupant (driver) only in the vehicle.

Q. Is the check result normal?

This diagnosis is complete.

Go to Step 2.

STEP 2. Check the parking brake.

Does the brake warning lamp remain on after the parking brake is released?

Q. Does the brake warning lamp remain on?

Proceed to the symptom procedure "The brake warning lamp does not go out (ABS warning lamp is OFF) although the parking brake is released" (Refer to

). Then go to Step 10.

Go to Step 3.

STEP 3. M.U.T.-III CAN bus diagnosis

Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

Go to Step 4.

Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting

). Then go to Step 10.

STEP 4. M.U.T.-III diagnosis code

Use M.U.T.-III to check the diagnosis code for the ASTC system.

Q. Is the diagnosis code set?

Follow the relevant diagnosis code procedure (Refer to

Go to Step 5.

STEP 5. M.U.T.-III data list

Evaluate the data list below.

Apply the parking brake.

Item No.	Item name	Normal conditions
30	Parking brake switch	Engage

Release the parking brake.

Item No.	Item name	Normal conditions
30	Parking brake switch	from "Engage" to "Disengage"

Move the selector lever to "R", "D", "N" and "P".

Item No.

Item name

Normal conditions

Target gear

Selector lever position: R

Selector lever position: D

Selector lever position: P

Selector lever position: N

Actual gear

Q. Is the check result normal?

YES

: Go to Step 6.

NO <item No. 30>

: Proceed to the symptom procedure "The brake warning lamp does not go out (ABS warning lamp is OFF) although the parking brake is released" (Refer to

). Then go to Step 10.

NO <item No. 14, 15>

: Go to Step 8.

STEP 6. M.U.T.-III data list

Evaluate the data list below with one person on the driver’s seat and the vehicle otherwise unloaded (unladen weight) on a smooth flat surface (Refer to

Item No. 05: Longitudinal G sensor
Item No. 06: Lateral G sensor

Q. Is the check result normal?

Go to Step 7.

Calibrate the G sensor (Refer to

). Then go to Step 10.

STEP 7. M.U.T.-III data list

Evaluate the data list (Refer to

Item No. 09: M/C pressure (Raw value)

Q. Is the check result normal?

Go to Step 8.

Go to Step 10.

STEP 8. M.U.T.-III Diagnosis code of other systems

Use M.U.T.-III to check if the diagnosis code is set in the A/T-ECU.

Q. Is the diagnosis code set?

Diagnose the A/T system (Refer to GROUP 23A - Troubleshooting

). Then go to Step 10.

Go to Step 9.

STEP 9. Retest the system

Check if the HSA works with one person on the driver’s seat.

Q. Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction

Replace the hydraulic unit assembly (integrated with ASTC-ECU) (Refer to

STEP 10. Retest the system

Check if the HSA works with one person on the driver’s seat.

Q. Is the check result normal?

This diagnosis is complete.

Replace the hydraulic unit assembly (integrated with ASTC-ECU) (Refer to