Inspection Procedure 9: Abnormality In Brake Operation
Inspection Procedure 9: Abnormality in brake operationCAUTION:
^ 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.
^ Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
^ When the hydraulic unit (integrated with ASC-ECU) is replaced, always perform the calibration of steering wheel sensor, G and yaw rate sensor, brake fluid pressure sensor, cut valve, and inlet valve.
TECHNICAL DESCRIPTION (COMMENT)
Although it is difficult to determine the trouble cause since it depends on the running status and road surface condition, a malfunction of hydraulic circuit may be present if no diagnostic trouble code is 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
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. Check the DTC.
Using scan tool, check the diagnostic trouble code for ASC system. (Refer to Diagnostic Trouble Code Descriptions.)
Q: Is the check result normal?
YES: Go to Step 2.
NO: Carry out the diagnosis for DTC. (Refer to Diagnostic Trouble Code Descriptions.)
STEP 2. Hydraulic unit (integrated with ASC-ECU) check
Check that the brake tube is correctly mounted to the hydraulic unit (integrated with ASC-ECU). (Refer to Testing and Inspection.)
Q: Is the check result normal?
YES: Go to Step 3.
NO: Connect the brake tubes correctly, and repair or replace the external brake lines of the hydraulic unit (integrated with ASC-ECU).
STEP 3. Brake operation check
Perform the following checks.
^ Brake pedal check (Refer to On-vehicle Service, Brake Pedal Check Brake Pedal Check and Adjustment.)
^ Brake booster check (Refer to On-vehicle Service, Brake Booster Operation Check Testing and Inspection.)
^ Check valve check (Refer to On-vehicle Service, Check Valve Operation Check Testing and Inspection.)
Q: Can any fault be found with the brake operation?
YES: Check the brake-related parts, and repair if necessary. Then, go to Step 4.
NO: Go to Step 4.
STEP 4. Hydraulic unit check
Perform the following actuator tests. (Refer to Actuator Test Reference Table.)
^ Item 01: FL wheel ABS drive
^ Item 02: FR wheel ABS drive
^ Item 03: RL wheel ABS drive
^ Item 04: RR wheel ABS drive
^ Item 05: FL wheel TCL drive
^ Item 06: FR wheel TCL drive
^ Item 07: RL wheel TCL drive
^ Item 08: RR wheel TCL drive
Q: Is the check result normal?
YES: The procedure is complete.
NO: Replace the hydraulic unit (incorporates in ASC-ECU).