Inspection Procedure 7: ABS system inoperative


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, Trouble code diagnosis ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.

COMMENTS ON TROUBLE SYMPTOM
In case of this trouble symptom, ABS system operation may be disabled. Diagnosis code may be set by the ABS system and so read the diagnosis code using M.U.T.-III.

PROBABLE CAUSES

  • Low battery voltage
  • Wiring harness or connector failure of CAN bus line
  • The ABS-ECU is defective.
  • Different ETACS-ECU, abnormal variant coding information

DIAGNOSTIC PROCEDURE

STEP 1. 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 2.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnosis 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. (Refer to .) Then go to Step 7.

STEP 3. Check the ABS-ECU power supply circuit.
Refer to .

Q. Is the check result normal?
Go to Step 4.
Carry out the diagnosis of ABS-ECU power supply circuit system.(Refer to .) Then go to Step 7.

STEP 4. 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 5.
Connect the brake tube correctly. Then go to Step 7.

STEP 5. ABS operation check

Q. Does the ABS work normally?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)
Check the brake system related components except ABS. Then go to Step 6.

STEP 6. ABS operation check

Q. Does the ABS work normally?
This diagnosis is complete.
Replace the hydraulic unit (integrated with ABS-ECU) (Refer to ). Then go to Step 7.

STEP 7. ABS operation check

Q. Does the ABS work normally?
This diagnosis is complete.
Return to Step 1.