Inspection Procedure 8:
TCL/ASC-ECU Power Supply Circuit System
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- When the TCL/ASC-ECU
power supply voltage becomes 9.7 ± 0.3 V or less, the ABS warning lamp and TCL/ASC
warning display, and the ABS and TCL/ASC controls are prohibited.
- If the battery terminal is not tightened properly, a dump surge may occur and the
power supply voltage may become abnormally high for a short time.
- 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, CAN Bus Diagnosis
Table
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- Whenever ECU is replaced, ensure that the CAN bus lines are normal.
- When the hydraulic unit (integrated with TCL/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 , and ).
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- TCL/ASC-ECU contains the power supply circuit (terminal No.44)
for the solenoid valve. The solenoid valve is energised by the valve relay, which is incorporated
in TCL/ASC-ECU.
- TCL/ASC-ECU contains the power supply circuit (terminal No. 40) for TCL/ASC-ECU.
When the ignition switch (IG1) is turned "ON", the voltage is supplied from the multi-purpose fuse
No. 12.
- When malfunction occurs in TCL/ASC-ECU power supply, the communication with M.U.T.-III
becomes unavailable.
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- Damaged wiring harness and connectors
- Fuse and fusible link malfunction
- Improper tightening of battery terminal
- Improper tightening of earth bolt
- Battery failure
- Charging system failed
- TCL/ASC-ECU malfunction
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Refer to GROUP 54A - Battery Test .
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Q.
Is the battery in good condition?
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 Go to Step 3.
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 Charge or replace the battery. Then go to Step 2.
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STEP 2. Charging system check
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Refer to GROUP 16 - Charging System <Except 4G1>, <4G1>.
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Q.
Is the charging system in good condition?
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Go to Step 3.
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Repair or replace the charging system component(s).
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STEP 3. Connector check: A-06 TCL/ASC-ECU connector, B-210 junction
block connector, B-229 junction block connector
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Q.
Is the check result normal?
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Go to Step 4.
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NO : Repair the damaged connector.
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STEP 4. Fusible link check: Check the fusible link No.5.
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Q.
Is the check result normal?
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Go to Step 6.
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Go to Step 5.
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STEP 5. Resistance measurement at A-06 TCL/ASC-ECU connector
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(1)Removal the fusible link No.5.
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(2)Disconnect the TCL/ASC-ECU connector, connect special tool ABS check harness (MB991984)
to the harness-side connector, and then measure the resistance at the special tool connector
side.
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Do not connect the special tool ABS check harness (MB991984) to TCL/ASC-ECU.
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(3)Resistance between the terminal No.44 and the body earth.
OK: No continuity
Q.
Is the check result normal?
Replace the fusible link No.5. Then go to Step 14.
The short circuit may be present in the power supply circuit. Repair the wiring
harness between the A-06 TCL/ASC-ECU connector terminal No.44 and the fusible link No.5, and
then replace the fusible link No.5. Then go to Step 14.
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STEP 6. Voltage measurement at the A-06 TCL/ASC-ECU connector
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(1)Disconnect the TCL/ASC-ECU connector, connect special tool ABS check harness (MB991984)
to the harness-side connector, and then measure the voltage at the special tool connector side.
| note |
Do not connect the special tool ABS check harness (MB991984) to TCL/ASC-ECU.
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(2)Measure the voltage between terminal No.44 and body earth.
OK: System voltage
Q.
Is the check result normal?
Go to Step 7.
The open circuit may be present in the power supply circuit. Repair the wiring
harness between the A-06 TCL/ASC-ECU connector terminal No.44 and the fusible link No.5. Then
go to Step 14.
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STEP 7. Check the fuse No.40.
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Visually check for open circuit in fuse No.40.
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Q.
Is the check result normal?
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Go to Step 9.
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Go to Step 8.
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STEP 8. Resistance measurement at A-06 TCL/ASC-ECU connector
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(1)Disconnect the B-210 junction block connector.
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(2)Disconnect the TCL/ASC-ECU connector, connect special tool ABS check harness (MB991984)
to the harness-side connector, and then measure the resistance at the special tool connector
side.
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Do not connect the special tool ABS check harness (MB991984) to TCL/ASC-ECU.
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(3)Resistance between the terminal No.40 and the body earth.
OK: No continuity
Q.
Is the check result normal?
Replace the fuse No.40. Then go to Step 14.
The short circuit may be present in the power supply circuit. Repair the wiring
harness between the A-06 TCL/ASC-ECU connector terminal No.40 and the B-210 junction block connector
terminal No.11, and then replace the fuse No.40. Then go to Step 14.
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STEP 9. Resistance measurement at A-06 TCL/ASC-ECU connector
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(1)Disconnect the B-210 junction block connector.
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(2)Disconnect the A-06 TCL/ASC-ECU connector, connect special tool ABS check harness
(MB991984) to the harness-side connector, and then measure the resistance at the special tool
connector side.
| note |
Do not connect the special tool ABS check harness (MB991984) to TCL/ASC-ECU.
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(3)Resistance between the A-06 TCL/ASC-ECU connector terminal No.40 and the B-210
junction block connector terminal No.11.
OK: Continuity exists (2 Ω or less)
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Q.
Is the check result normal?
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Go to Step 10.
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The open circuit may be present in the power supply circuit. Repair the wiring
harness between the A-06 TCL/ASC-ECU connector terminal No.40 and the B-210 junction block connector
terminal No.11. Then go to Step 14.
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STEP 10. Measure the voltage at the B-229 junction block connector.
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(1)Measure by backprobing without disconnecting the connector.
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(2)Turn the ignition switch to the "ON" position.
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(3)Measure the voltage between the terminal No.3 and the body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 12.
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Go to Step 11.
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STEP 11. Resistance measurement at B-229 junction block connector
and the B-240 ignition switch connector
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(1)Disconnect the B-229 junction block connector and B-240 ignition switch connector,
and then measure the resistance at the harness connector side.
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(2)Resistance between the B-229 junction block connector terminal No.3 and B-240 ignition
switch connector terminal No.2.
OK: Continuity exists (2 Ω or less)
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Q.
Is the check result normal?
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Go to Step 12.
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The open circuit may be present in the power supply circuit. Repair the wiring
harness between the B-229 junction block connector terminal No.3 and B-240 ignition switch connector
terminal No.2. Then go to Step 14.
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STEP 12. Resistance measurement at A-06 TCL/ASC-ECU connector
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(1)Disconnect the TCL/ASC-ECU connector, connect special tool ABS check harness (MB991984)
to the harness-side connector, and then measure the resistance at the special tool connector
side.
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Do not connect the special tool ABS check harness (MB991984) to TCL/ASC-ECU.
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(2)Resistance between the terminal No.43 and the body earth, and between the terminal
No.46 and the body earth.
OK: Continuity exists (2 Ω or less)
Q.
Is the check result normal?
Go to Step 13.
An open circuit may be present in the earth circuit. Repair the wiring harness
between the A-06 TCL/ASC-ECU connector terminal No.43 and the body earth, and between the A-06
TCL/ASC-ECU connector terminal No.46 and the body earth.
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STEP 13. Retest the system.
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Q.
Is the communication with M.U.T.-III possible?
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Replace the hydraulic unit (integrated with TCL/ASC-ECU) (Refer to ). Then
go to Step 14.
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunction .)
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STEP 14. Retest the system.
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Q.
Is the communication with M.U.T.-III possible?
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Return to Step 1.
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This diagnosis is complete.
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