Inspection Procedure 1

Inspection Procedure 1: Scan tool communication with ABS/ASC system is impossible.

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 CAN Bus Line Diagnostics Flow ).
- Whenever ECU is replaced, ensure that the CAN bus lines are normal.
- If the power is supplied with the ground circuit of CAN communication device open circuited, an electric potential abnormality may occur to the CAN bus lines.
- 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 Active Stability Control System (ASC) , Active Stability Control System (ASC) and Active Stability Control System (ASC) ).

COMMENTS ON TROUBLE SYMPTOM

When scan tool cannot communicate with the ABS/ASC system, the CAN bus lines, ASC-ECU power supply circuit system, ground, or ASC-ECU may be faulty.

PROBABLE CAUSES

- Damaged wiring harness and connectors
- ASC-ECU malfunction
- Wrong routing of scan tool harness
- Abnormality in battery or generator
- Abnormality in power supply voltage to ASC-ECU
- ECU malfunction of other system

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

Scan tool CAN bus diagnosis

Use scan tool to diagnose the CAN bus lines.

Q. Is the check result normal?

YES Check the power supply circuit, and repair if necessary (Refer to Inspection Procedure 12).
NO Repair the CAN bus lines CAN Bus Diagnostics Chart).