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 stored. 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.

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 and yaw rate sensor or brake fluid pressure sensor.
  • The parking brake switch may be seized, which causes the HSA to fail to start the operation.
  • A problem (noise interference) may have occurred in the CAN bus line, resulting in an improper communication with ASC-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 and yaw rate sensor
  • Calibration failure of the brake fluid pressure sensor
  • Seizure of the parking brake switch
  • Malfunction of wheel speed sensor
  • Malfunction of ETACS-ECU
  • Malfunction of hydraulic unit (integrated with ASC-ECU)
  • Wiring harness or connector failure of CAN bus line
  • Damaged wiring harness and connectors

DIAGNOSIS PROCEDURE


STEP 1. HSA operation 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. Parking brake check


With the parking brake not pulled, check if the brake warning lamp is off.

Q. Is the check result normal?

Go to Step 3.
Carry out Inspection procedure 3 "Brake warning lamp stays ON with the parking brake lever released (ABS warning lamp is OFF)" (Refer to ).

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


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

Q. Is the check result normal?

Go to Step 4.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ). Then go to Step 9.

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 stored?

Carry out the diagnosis for the diagnosis code (Refer to ).
Go to Step 5.

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


Check the following data list (Refer to GROUP 54D ).

  • Pull the parking brake lever with the electric parking brake switch ON.

<PHEV-ECU>
Item No.
Item name
Normal condition
4
Parking brake switch
ON

  • Operate the selector lever.

<PHEV-ECU>
Item No.
Item name
Normal condition
303
Shift position (for control)
Displays a selector lever position

Q. Is the check result normal?

Go to Step 6.
NO <Item No. 4> : Carry out the Inspection procedure 3 "Brake warning lamp stays ON with the parking brake lever released (ABS warning lamp is OFF)" (Refer to ), and then go to Step 10.
NO <Item No. 303> : Go to Step 9.

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


Check the following data list under curb weight condition or one occupant (driver) only in the vehicle, on a flat road.(Refer to )

  • Item 09: G sensor
  • Item 12: Yaw rate sensor

Q. Is the check result normal?

Go to Step 7.
Carry out the calibration of the G and yaw rate sensor (Refer to ). Then go to Step 9.

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


Check the following data list (Refer to ).

  • Item 10: Master cylinder pressure

Q. Is the check result normal?

Go to Step 8.
Carry out the calibration of the brake fluid pressure sensor (Refer to ). Then go to Step 10.

STEP 8. M.U.T.-III diagnosis code


Use M.U.T.-III to check whether the diagnosis code is stored in the PHEV-ECU (related to the parking lock and clutch proportional valve).

Q. Is the diagnosis code stored?

Carry out the diagnosis for the diagnosis code (Refer to GROUP 54D - Troubleshooting/Diagnosis Code Chart ).
Go to Step 9.

STEP 9. Retest the system.


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

Q. Is the check result normal?

Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ).

STEP 10. Retest the system.


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

Q. Is the check result normal?

This diagnosis is complete.
Return to Step 1.