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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 diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.
  • When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor (Refer to , and ).
 
 
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
  • Improper installation of the G and yaw rate sensor
  • G and yaw rate sensor 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
The procedure is complete.
 
STEP 2. Using scan tool MB991958, check the data list
Check the following data list (Refer to ).
  • Item 09: G Sensor
Is the check result normal?
Go to Step 4.
Go to Step 3
 
STEP 3. Brake drag check
Check the brake system for drag.
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?
Return to Step 2.
The procedure is complete.