Inspection Procedure 12

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

CAUTION: Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.

CAN Box Unit Power Supply Circuit (Part 1):

CAN Box Unit Power Supply Circuit (Part 2):

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-108 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is CAN box unit connectors C-108 in good condition?

YES : Go to Step 2.

NO : Repair or replace the damaged component(s). Refer to general (electrical), Harness Connector Inspection.

STEP 2. Check the ground circuit to the CAN box unit. Measure the resistance at CAN box unit connector C-108.

1. Disconnect CAN box unit connector C-108 and measure the resistance available at the wiring harness side of the connector.




2. Measure the resistance value between CAN box unit connector C-108 terminal 1 and ground.

OK: 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-108 (terminal 1) and the ground.

NOTE: Also check intermediate connector C-105 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-105 is damaged, repair or replace the connector as described in general (electrical), Harness Connector Inspection.

Q: Is the wiring harness between CAN box unit connector C-108 (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-108.

1. Disconnect CAN box unit connectors C-108 measure the voltage available at the wiring harness side of the connector.




2. Measure the voltage between CAN box unit connector C-108 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-108 (terminal 2) and fusible link (36).

NOTE: Also check intermediate connector C-105 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-105 or ETACS-ECU connector C-307 or C-317 is damaged, repair or replace the connector as described in general (electrical) Harness Connector Inspection.

Q: Is the wiring harness between CAN box unit connector C-108 (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. Check the wiring harness between CAN box unit connector C-108 (terminal 10) and fusible link (37).

NOTE: Also check joint connector C-07, intermediate connector C-105 and ETACS-ECU connectors C-309 and C-315 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-07, intermediate connector C-105 or ETACS-ECU connectors C-309 or C-315 is damaged, repair or replace the connector as described in general (electrical), Harness Connector Inspection.

Q: Is the wiring harness between CAN box unit connector C-108 (terminal 10) and fusible link (37) 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.