Inspection Procedure 16: HSA (Hill Start Assist) works on a flat road.

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 - CAN Bus Diagnostics Table ).
Whenever ECU is replaced, ensure that the CAN bus lines are normal.
When the hydraulic unit (integrated with ASTC-ECU) is replaced, always carry out the calibration of the master cylinder pressure sensor, steering wheel sensor and the G and yaw rate sensor (Refer to ).

COMMENTS ON TROUBLE SYMPTOM

A failure may have occurred in the calibration of the G & yaw rate sensor.
Some drivers mistake a brake dragging for HSA operation.
If the suspension is modified, the vehicle posture changes, and the ASTC-ECU judges that the vehicle is on a steep slope and may activate HSA.

PROBABLE CAUSES

The G and yaw rate sensor improperly calibrated
Brake drag

DIAGNOSIS PROCEDURE

STEP 1. HSA function check

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

Q. Does the HSA work on a flat road?

	Go to Step 2.

	This diagnosis is complete.

STEP 2. 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. 19: Longitudinal G sensor (Raw value)

Q. Is the check result normal?

	Go to Step 4.

	Go to Step 3.

STEP 3. Check the brake system for brake drag.

Check the brake system for brake drag.

Q. Is the check result normal?

	Go to Step 4.

	Repair the brake drag. Then go to Step 4.

STEP 4. Retest the system

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

Q. Does the HSA work on a flat road?

	Return to Step 2.

	This diagnosis is complete.