Inspection Procedure 7: ABS System Inoperative

Inspection Procedure 7: ABS System Inoperative.

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.
^ 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. DTC may be set by the ABS system using scan tool.

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

DIAGNOSIS

Required Special Tools:
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A

STEP 1. M.U.T.-III CAN bus diagnostics
Use scan tool to diagnose the CAN bus lines.

Q: Is the check result normal?
YES: Go to Step 2.
NO: Repair the CAN bus lines. On completion, go to Step 2.

STEP 2. DTC check
Use scan tool to check the DTC for the ABS system.

Q: Is the check result normal?
YES: Go to Step 3.
NO: Carry out the diagnosis for the DTC. Then go to Step 7.

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

Q: Is the check result normal?
YES: Go to Step 4.
NO: Carry out the diagnosis of ABS-ECU power supply circuit system. 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).

Q: Is the check result normal?
YES: Go to Step 5.
NO: Connect the brake tube correctly. Then go to Step 7.

STEP 5. Operation check

Q: Does the ABS work normally?
YES: Intermittent malfunction.
NO: Check the brake system related components except ABS. Then go to Step 6.

STEP 6. Operation check

Q: Does the ABS work normally?
YES: The procedure is complete.
NO: Replace the hydraulic unit (integrated with ABS-ECU). Then go to Step 7.

STEP 7. Operation check

Q: Does the ABS warning light turn ON and OFF normally?
YES: The procedure is complete.
NO: Return to Step 1.