Symptom Procedures

Malfunction of ETACS-ECU power supply circuit










TECHNICAL DESCRIPTION (COMMENT)

If the ETACS-ECU functions do not work at all, the ETACS-ECU power supply system, ground system, or ETACS-ECU may have a problem.

TROUBLESHOOTING HINTS

- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
- The ETACS-ECU may be defective

DIAGNOSIS

Required Special Tools:

- MB991223: Harness Set
- MB992006: Extra Fine Probe

STEP 1. Check ETACS-ECU connectors C-315 and C-317 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is ETACS-ECU connectors C-315 and C-317 in good condition?

YES Go to Step 2.
NO Repair or replace the damaged component(s) Harness Connector Inspection).
STEP 2. Check the ground circuit to the ETACS-ECU. Measure the resistance at ETACS-ECU connectors C-315 and C-317.

(1)Disconnect ETACS-ECU connector C-315 and C-317 and measure the resistance available at the wiring harness side of the connector.





(2)Measure the resistance value between ETACS-ECU connector C-315 terminal 17 and ground.

- The resistance should be 2 ohms or less.





(3)Measure the resistance value between ETACS-ECU connector C-317 terminal 15 and ground.

- The resistance should be 2 ohms or less.

Q. Is the measured resistance 2 ohms or less?

YES Go to Step 4.

NO Go to Step 3.

STEP 3. Check the wiring harness between ETACS-ECU connector C-315
(terminal 17) or C-317 (terminal 15) and the ground.

- Check the ground wires for open circuit.

Q. Is the wiring harness between ETACS-ECU connector C-315 (terminal 17) or C-317 (terminal 15) and the ground in good condition?

YES No action is necessary and testing is complete.
NO The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary.
STEP 4. Check ETACS-ECU connectors C-307 and C-309 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is ETACS-ECU connectors C-307 and C-309 in good condition?

YES Go to Step 5.
NO Repair or replace the damaged component(s) Harness Connector Inspection).
STEP 5. Check the battery power supply circuit to the ETACS-ECU. Measure the voltage at ETACS-ECU connectors C-307 and C-309.

(1)Disconnect ETACS-ECU connectors C-307 and C-309 measure the voltage available at the wiring harness side of the connector.





(2)Measure the voltage between ETACS-ECU connector C-307 terminal 2 and ground.

- The voltage should measure approximately 12 volts (battery positive voltage).





(3)Measure the voltage between ETACS-ECU connector C-309 terminal 1 and ground.

- The voltage should measure approximately 12 volts (battery positive voltage).

Q. Is the measured voltage approximately 12 volts (battery positive voltage)?

YES Go to Step 7.

NO Go to Step 6.

STEP 6. Check the wiring harness between ETACS-ECU connectors C-307
(terminal 2) or C-309 (terminal 1) and the fusible link (36) or (34).

- Check the power supply line (battery supply) for open circuit and short circuit.

Q. Is the wiring harness between ETACS-ECU connectors C-307 (terminal 2) or C-309 (terminal 1) and the fusible link (36) or (34) in good condition?

YES No action is necessary and testing is complete.
NO The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The system should communicate with the ETACS-ECU normally.
STEP 7. Retest the system

Check that the ETACS-ECU functions work normally.

Q. Is the check result satisfactory?

YES The procedure is complete (If no malfunctions are found in all steps, an intermittent malfunction is suspected. How to Cope With Intermittent Malfunctions).
NO Replace the ETACS-ECU.