Inspection Procedure 6: Abnormality in brake operation


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.

COMMENTS ON TROUBLE SYMPTOM
Although the cause of the trouble cannot be clearly resolved since it depends on the running status and road surface condition, the malfunction of the hydraulic circuit may occur if any diagnosis code is not detected.

PROBABLE CAUSES

  • Malfunction of hydraulic unit (integrated with ABS-ECU)
  • Malfunction of hydraulic circuit
  • Malfunction of brake assembly
  • Malfunction of brake booster
  • Malfunction of master cylinder assembly

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis
Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ). On completion, go to Step 2.

STEP 2. Diagnosis code check
Use M.U.T.-III to check the diagnosis code for the ABS system (Refer to ).

Q. Is the check result normal?
Go to Step 3.
Carry out the diagnosis for the diagnosis code chart (Refer to ).

STEP 3. Hydraulic unit (integrated with ABS-ECU) check
Check that the brake tube is correctly mounted to the hydraulic unit (integrated with ABS-ECU) (Refer to ).

Q. Is the check result normal?
Go to Step 4.
Connect the brake tubes correctly, and repair or replace the external brake lines of the hydraulic unit (integrated with ABS-ECU).

STEP 4. Brake operation check
Perform the following checks.

  • Brake pedal check (Refer to GROUP 35A - On-vehicle Service/Brake Pedal Check ).
  • Brake booster check (Refer to GROUP 35A - On-vehicle Service/Brake Booster Operation Check ).
  • Check valve check (Refer to GROUP 35A - On-vehicle Service/Check Valve Operation Check ).

Q. Can any fault be found with the brake operation?
Check the brake-related parts, and repair if necessary. Then, go to Step 5.
Go to Step 5.

STEP 5. Hydraulic unit check
Perform the following actuator tests (Refer to ).

  • Item No.01: FL wheel ABS
  • Item No.02: FR wheel ABS
  • Item No.03: RL wheel ABS
  • Item No.04: RR wheel ABS

Q. Is the check result normal?
This diagnosis is complete.
Replace the hydraulic unit (integrated with ABS-ECU) (Refer to ).