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Inspection Procedure 15: HSA (Hill Start Assist) works on a flat road.
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect DTC 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.
 
 
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 ASC-ECU judges that the vehicle is on a steep slope and may activate HSA.
 
 
 
PROBABLE CAUSES
  • ASC-ECU malfunction
  • Brake drag
  • Damaged wiring harness and connectors
 
 
 
 
DIAGNOSIS
STEP 1. HSA operation check.
Check if the HSA works on a flat road with one occupant (driver) only in the vehicle.
Does the HSA work on a flat road?
Go to Step 2.
This diagnosis is complete.
 
STEP 2. Using scan tool (M.U.T.-IIISE), check data list
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ."
(2) Check the following data list (Refer to ).
Item 09: G sensor
Is the check result normal?
Go to Step 3.
Carry out the calibration of the G and yaw rate sensor (Refer to ). Then go to Step 4.
 
STEP 3. Brake drag check.
Check the brake system for drag (Refer to GROUP 35A - On vehicle service/Brake drag force check ).
Is the check result normal?
Go to Step 4.
Repair the brake drag, and then go to Step 4.
 
STEP 4. Retest the system.
Check if the HSA works on a flat road with one occupant (driver) only in the vehicle.
Does the HSA work on a flat road?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ).
This diagnosis is complete.