Inspection Procedure 15: 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 - 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



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



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.
Check whether the parking brake warning lamp remains on with the parking brake lever not pulled up.

Q. Does the parking brake warning lamp remain on?
Proceed to the symptom procedure "Brake warning lamp stays ON with the parking brake lever released (ABS warning lamp is OFF)", . 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 ASC 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.

  • Pull the parking brake lever.
Item No.
 Item name
 Normal conditions
18
 Parking brake switch
 ON

  • Release the parking brake lever.
Item No.
 Item name
 Normal conditions
18
 Parking brake switch
 from ON to OFF

  • Move the selector lever to "R", "D", "N" and "P".
Item No.
 Item name
 Normal conditions
10
 Target gear
  • "R"

    • Selector lever position: R

  • "D"

    • Selector lever position: D

  • "P"

    • Selector lever position: P

  • "N"

    • Selector lever position: N
11
 Actual gear

Q. Is the check result normal?
YES : Go to Step 6.
NO <item No. 18> : Proceed to the symptom procedure "Brake warning lamp stays ON with the parking brake lever released (ABS warning lamp is OFF)", . Then go to Step 10 .
NO <item No. 10, 11> : 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. 19: Longitudinal G sensor (Raw value)
  • Item No. 20: Lateral G sensor (Raw value)

Q. Is the check result normal?
Go to Step 7.
Calibrate the G and yaw rate sensor (Refer to ). Then go to Step 10.

STEP 7. M.U.T.-III data list
Evaluate the data list (Refer to ).

  • Item No. 22: 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.
Return to Step 1.