Inspection Procedure 2: TCL/ASC-ECU power supply system




OPERATION

  • The TCL/ASC-ECU is energized by the ignition switch (IG1) through multi-purpose fuse No.40 and the TCL/ASC-ECU terminal No.40.
  • If the power supply to the TCL/ASC-ECU has failed, M.U.T.-III will not be able to communicate with it.

PROBABLE CAUSES

  • Damaged wiring harness or connector
  • Defective battery
  • Charging system failed
  • Malfunction of the hydraulic unit (integrated with TCL/ASC-ECU)

DIAGNOSIS PROCEDURE

STEP 1. Voltage measurement at the battery terminal
(1)Ignition switch: "ON"
(2)Engine: Started
(3)Measure the voltage between the battery terminals.
OK: more than 10 V

Q. Is the check result normal?
Go to Step 2.
Diagnose the charging system (Refer to GROUP 16, Charging System - On-vehicle Service ).

STEP 2. Connector check: A-06 TCL/ASC-ECU connector

Q. Is the check result normal?

Go to Step 3.

Repair the defective connector.

STEP 3. Voltage measurement at the A-06 TCL/ASC-ECU connector.

(1)Disconnect the A-06 TCL/ASC-ECU connector, and connect special tool ABS Check Harness (MB991984) to the wiring harness-side connector.
note Connect special tool ABS Check Harness (MB991984) to the TCL/ASC-ECU.
(2)Ignition switch: "ON"
(3)Engine: Started

(4)Voltage between special tool ABS Check Harness (MB991984) connector terminal No.40 and body earth
OK: More than 10 V

Q. Is the check result normal?

Go to Step 4.

Repair the wiring harness between A-06 TCL/ASC-ECU connector terminal No. 40 and the ignition switch (IG1).

STEP 4. Resistance measurement at the A-06 TCL/ASC-ECU connector.

(1)Disconnect the A-06 TCL/ASC-ECU connector, and connect special tool ABS Check Harness (MB991984) to the wiring harness-side connector.
note Do not connect special tool ABS Check Harness (MB991984) to the TCL/ASC-ECU.

(2)Measure the resistance between the A-06 TCL/ASC-ECU connector terminal No.43 and body earth and between the A-06 TCL/ASC-ECU connector terminal No.46 and body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Go to Step 5.

Repair the wiring harness between A-06 TCL/ASC-ECU connector terminal No.43 and body earth.

STEP 5. Retest the system.

Q. Can the TCL/ASC-ECU communicate with the M.U.T.-III?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .
Replace the hydraulic unit (integrated with TCL/ASC-ECU). Then perform the variant coding and write the VIN data (Refer to GROUP 00, Precautions Before Service - How to Perform Variant Coding ).