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Inspection Procedure 12




Inspection Procedure 12: Check the CAN box unit power supply circuit.

CAUTION:
Whenever the CAN box unit is replaced, ensure that the power supply circuit and the grounding circuit are normal. (Check that the voltage is 10 V or more.)













TECHNICAL DESCRIPTION (COMMENT)

If the CAN box unit functions do not work at all, the CAN box unit power supply system, ground system, or CAN box unit 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 CAN box unit may be defective

DIAGNOSIS

Required Special Tools:

- MB991223: Harness Set

- MB992006: Extra Fine Probe

STEP 1. Check CAN box unit connectors C-13 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is CAN box unit connectors C-13 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 CAN box unit. Measure the resistance at CAN box unit connectors C-13.

(1)Disconnect CAN box unit connector C-13 and measure the resistance available at the wiring harness side of the connector.





(2)Measure the resistance value between CAN box unit connector C-13 terminal 1 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 CAN box unit connector C-13
(terminal 1) and the ground.

- Check the ground wires for open circuit.

Q. Is the wiring harness between CAN box unit connector C-13 (terminal 1) 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 the battery power supply circuit to the CAN box unit.
Measure the voltage at CAN box unit connectors C-13.

(1)Disconnect CAN box unit connectors C-13 measure the voltage available at the wiring harness side of the connector.





(2)Measure the voltage between CAN box unit connector C-13 terminal 2 and ground.

- OK: 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 6.

NO Go to Step 5.

STEP 5. Check the wiring harness between CAN box unit connector C-13
(terminal 2) and fusible link (36).

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

NOTE:
Also check intermediate connector C-17 and ETACS-ECU connectors C-307 and C-317 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-17 and ETACS-ECU connector C-307 or C-317 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

Q. Is the wiring harness between CAN box unit connector C-13 (terminal 2) and fusible link (36) 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 CAN box unit normally.
STEP 6. Using scan tool MB991958, check data list.

Check the input signal of ACC relay.

- Turn the ignition switch to the ACC position.





OK: Normal condition is displayed.

Q. Is the check result normal?

YES Go to Step 7.
NO Inspection Procedure 1."
STEP 7. Check the battery power supply circuit to the CAN box unit.
Measure the voltage at CAN box unit connector C-13.

(1)Disconnect CAN box unit connectors C-13 measure the voltage available at the wiring harness side of the connector.





(2)Measure the voltage between CAN box unit connector C-13 terminal 10 and ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Q. Is the measured voltage approximately 12 volts (battery positive voltage)?

YES Replace the CAN box unit.

NO Go to Step 8.

STEP 8. Voltage measurement at C-309 ETACS-ECU connector. Check the battery power supply circuit to the ETACS-ECU. Measure the voltage at ETACS-ECU connector C-309.

(1)Disconnect the connector, and measure at the wiring harness-side connector.

(2)Measure the voltage between C-309 ETACS-ECU connector terminal 2 and ground.
OK: 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 9.
NO Go to Step 11.
STEP 9. Check ETACS-ECU connector C-315 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is ETACS-ECU connector C-315 in good condition?

YES Go to Step 10.
NO Repair or replace the damaged component(s). Harness Connector Inspection.
STEP 10. Check the wiring harness between CAN box unit connectors C-13 (terminal 10) and ETACS-ECU connector C-315 (terminal 9).

NOTE:
Also check intermediate connector C-17 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-17 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

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

Q. Is the wiring harness between CAN box unit connectors C-13 (terminal 10) and ETACS-ECU connector C-315 (terminal 9) in good condition?

YES The trouble can be an intermittent malfunction How to Cope With Intermittent Malfunctions).
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 11. Check ETACS-ECU connector C-309 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is ETACS-ECU connector C-309 in good condition?

YES Go to Step 12.
NO Repair or replace the damaged component(s). Harness Connector Inspection.
STEP 12. Check the wiring harness between ETACS-ECU connector C-309
(terminal 2) and fusible link (37).

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

Q. Is the check result normal?

YES Replace the ETACS-ECU.
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.
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