Inspection Procedure 8: ABS-ECU power supply circuit system

OPERATION

The ABS-ECU power supply signal energized by the ignition switch (IG1) is transmitted to ABS-ECU (terminal No.7) via the multi-purpose fuse No.12.
The ABS-ECU power supply and the valve power supply are transmitted to ABS-ECU (terminal No.26) via the fusible link No.27.
The ABS-ECU power supply and the motor power supply are transmitted to ABS-ECU (terminal No.13) via the fusible link No.26.
When malfunction occurs in ABS-ECU power supply, the communication with M.U.T.-III becomes unavailable.

PROBABLE CAUSES

Damaged wiring harness and connectors
Blown fuse
Battery failure
Charging system failed
ABS-ECU malfunction

DIAGNOSIS PROCEDURE

STEP 1. Battery check

Refer to GROUP 54A - Battery Test

Q. Is the battery in good condition?

	Go to Step 2.

	Charge or replace the battery.

STEP 2. Charging system check

Refer to GROUP 16 - Charging System

(2000),

(2200),

(2400) or

(3000).

Q. Is the charging system in good condition?

	Go to Step 3.

	Repair or replace the charging system component(s).

STEP 3. Voltage measurement at the A-02 ABS-ECU connector

(1)Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) 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 (MB991974) to ABS-ECU.

(2)Turn the ignition switch to the ON position.
(3)Measure the voltage between terminal No.7 and body earth.
OK: Approximately battery voltage

Q. Is the check result normal?

Go to Step 4.

Go to Step 10.

STEP 4. Voltage measurement at the A-02 ABS-ECU connector

(1)Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) 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 (MB991974) to ABS-ECU.

(2)Measure the voltage between the terminal No.26 and the body earth.
OK: Approximately battery voltage

Q. Is the check result normal?

Go to Step 7.

Go to Step 5.

STEP 5. Check the fusible link No.27

Q. Is the check result normal?

	Go to Step 6.

	Replace the fusible link No.27.

STEP 6. Connector check: A-02 ABS-ECU connector

Q. Is the check result normal?

	Repair the wiring harness between the fusible link No.27 and the A-02 ABS-ECU connector terminal No.26.

	Repair the defective connector.

STEP 7. Voltage measurement at the A-02 ABS-ECU connector

(1)Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) 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 (MB991974) to ABS-ECU.

(2)Voltage between the terminal No.13 and the body earth
OK: Approximately battery voltage

Q. Is the check result normal?

Go to Step 19.

Go to Step 8.

STEP 8. Check the fusible link No.26

Q. Is the check result normal?

	Go to Step 9.

	Replace the fusible link No.26.

STEP 9. Connector check: A-02 ABS-ECU connector

Q. Is the check result normal?

	Repair the wiring harness between the fusible link No.26 and the A-02 ABS-ECU connector terminal No.13.

	Repair the defective connector.

STEP 10. Check the fuse No.12 and fusible link No.33

Q. Is the check result normal?

	Go to Step 11.

	Replace the abnormal fuse or fusible link.

STEP 11. Connector check: C-309 ETACS-ECU connector

Q. Is the check result normal?

	Go to Step 12.

	Repair the defective connector.

STEP 12. Voltage measurement at the C-309 ETACS-ECU connector

(1)Disconnect the ETACS-ECU connector, and then measure the voltage at the harness connector side.

(2)Voltage between the terminal No.1 and the body earth
OK: Approximately battery voltage

Q. Is the check result normal?

	Go to Step 13.

	Repair the wiring harness between the fusible link No.33 and the C-309 ETACS-ECU connector terminal No.1.

STEP 13. Connector check: C-317 ETACS-ECU connector

Q. Is the check result normal?

	Go to Step 14.

	Repair the defective connector.

STEP 14. Voltage measurement at the C-317 ETACS-ECU connector

(1)Disconnect the ETACS-ECU connector, and then measure the voltage at the ETACS-ECU side.

(2)Turn the ignition switch to the ON position.

(3)Voltage between the terminal No.6 and the body earth
OK: Approximately battery voltage

Q. Is the check result normal?

	Go to Step 16.

	Go to Step 15.

STEP 15. Connector check: C-210 ignition switch connector

Q. Is the check result normal?

	Go to Step 20.

	Repair the wiring harness between the C-210 ignition switch connector terminal No.2 and the C-317 ETACS-ECU connector terminal No.6.

STEP 16. Voltage measurement at the C-317 ETACS-ECU connector

(1)Do not disconnect the ETACS-ECU connector, and then measure the voltage for back probing.

(2)Turn the ignition switch to the ON position.

(3)Voltage between the terminal No.5 and the body earth
OK: Approximately battery voltage

Q. Is the check result normal?

	Go to Step 17.

	Replace ETACS-ECU (Refer to GROUP 54A - ETACS-ECU ).

STEP 17. Connector check: A-02 ABS-ECU connector, C-37 intermediate connector and C-317 ETACS-ECU connector

Q. Is the check result normal?

	Go to Step 18.

	Repair the defective connector.

STEP 18. Wiring harness check between the A-02 ABS-ECU connector terminal No.7 and C-317 ETACS-ECU connector terminal No.5

Check for open or short circuit.

Q. Is the check result normal?

	Go to Step 19.

	Repair the wiring harness.

STEP 19. Resistance measurement at A-02 ABS-ECU connector

(1)Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991974) 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 (MB991974) to ABS-ECU.

(2)Resistance between the terminal No.1 and the body earth, and between the terminal No.14 and the body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

Go to Step 20.

Repair the wiring harness.

STEP 20. Retest the system.

Q. Is the communication with M.U.T.-III possible?

	Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

	Make sure that the M.U.T.-III cable is properly connected and the V.C.I. switch is ON, and then replace ABS-ECU (Refer to ).