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Diagnostic Item 4: Diagnose shorts between CAN_H and L lines (CAN-C)
 
 
cautionWhen servicing a CAN bus line, ground yourself by touching a metal object such as an unpainted water pipe. If you fail to do, a component connected to the CAN bus line may be broken.
 
 
TROUBLE JUDGMENT
When all of the following conditions are met, the scan tool (M.U.T.-IIISE) determines that a short circuit is present between CAN_L and CAN_H lines.
  • The scan tool (M.U.T.-IIISE) cannot receive the periodic transmission data from any ECUs.
  • The voltage between CAN-C (CAN_L and CAN_H lines) is 1.0 V or more, 4.0 V or less.
  • The resistance at CAN-C (CAN_L and CAN_H lines) is 2 ohms or less.
 
 
TROUBLESHOOTING HINTS
  • Damaged harness wires and connectors
  • Malfunction of the ETACS-ECU
  • Malfunction of the PHEV-ECU
  • Malfunction of the gateway-ECU <Vehicles with Blind Spot Warning [BSW] (with Lane Change Assist) system>
  • Malfunction of the SRS-ECU
  • Malfunction of the column switch assembly (steering wheel sensor)
  • Malfunction of the occupant classification-ECU
  • Malfunction of the electric parking brake ECU
  • Malfunction of the FCM/LDW/AHB-ECU <Vehicles with FCM>
  • Malfunction of the ACC-ECU <Vehicles with ACC>
  • Malfunction of the EPS-ECU
  • Malfunction of the ASC-ECU
  • Malfunction of the engine control module (ECM)
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Connector check: C-126 intermediate connector.
cautionThe strand end of the twist wire should be within 10 cm (4 inches) from the connector. For details refer to .
Is the check result normal?
Go to Step 2.
Repair the defective connector.
 
STEP 2. Resistance measurement at C-126 intermediate connector.
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect the connector, and measure at its female-side intermediate connector (at the front wiring harness side).
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between C-126 intermediate connector terminal Nos.15 and 16
OK: 120 ± 20 ohms
Is the check result normal?
<Within 120 ± 20 ohms> Go to Step 15.
<Not within 120 ± 20 ohms> Go to Step 3.
 
STEP 3. Connector check: joint connector (CAN1) and joint connector (CAN2).
cautionThe strand end of the twist wire should be within 10 cm (4 inches) from the connector. For details refer to .
When checking the joint connector, ensure that its wiring harness side and its short pins are not damaged.
Is the check result normal?
Go to Step 4.
Repair a defective connector or replace the joint connector.
 
STEP 4. Resistance measurement at joint connector (CAN1).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN1) terminal Nos.2 and 11
OK: 120 ± 20 ohms
Is the check result normal?
: <Within 120 ± 20 ohms> Go to Step 9.
<Not within 120 ± 20 ohms> Go to Step 5.
 
STEP 5. Resistance measurement at joint connector (CAN2).
noteStep 5 and 6 are only for vehicles with ACC. On vehicles without it, go to Step 7.
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN2) terminal Nos.3 and 14
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 7.
<Less than 1 kΩ> Go to Step 6.
 
STEP 6. Resistance measurement at ACC-ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the ACC-ECU, and measure at the equipment side.
(2) Resistance between ACC-ECU connector terminal Nos.2 and 7
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN2) and the ACC-ECU connector.
<Less than 1 kΩ> Check the ACC-ECU connector, and repair if necessary. If the ACC-ECU connector is in good condition, replace the ACC-ECU.
 
STEP 7. Resistance measurement at joint connector (CAN2).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN2) terminal Nos.2 and 13
OK: 120 ± 20 ohms
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
: <Within 120 ± 20 ohms> Repair the wiring harness between joint connector (CAN2) and the joint connector (CAN1).
<Not within 120 ± 20 ohms> Go to Step 8.
 
STEP 8. Resistance measurement at ECM connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the ECM, and measure at the equipment side.
(2) Resistance between ECM connector terminal Nos.90 and 91
OK: 120 ± 20 ohms
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<Within 120 ± 20 ohms> Repair the wiring harness between joint connector (CAN2) and the ECM connector.
<Not within 120 ± 20 ohms> Check the ECM connector, and repair if necessary. If the ECM connector is in good condition, replace the ECM.
 
STEP 9. Resistance measurement at joint connector (CAN1).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN1), and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN1) terminal Nos.5 and 14
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 11.
<Less than 1 kΩ> Go to Step 10.
 
STEP 10. Resistance measurement at PHEV-ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the PHEV-ECU, and measure at the equipment side.
(2) Resistance at PHEV-ECU connector terminal Nos.17 and 16
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN1) and the PHEV-ECU connector.
<Less than 1 kΩ> Check the PHEV-ECU connector, and repair if necessary. If the PHEV-ECU connector is in good condition, replace the PHEV-ECU.
 
STEP 11. Resistance measurement at joint connector (CAN1).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN1) terminal Nos.4 and 13
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 13.
<Less than 1 kΩ> Go to Step 12.
 
STEP 12. Resistance measurement at EPS-ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the EPS-ECU, and measure at the equipment side.
(2) Resistance between EPS-ECU connector terminal Nos.5 and 6
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Check the intermediate connector, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between joint connector (CAN1) and the EPS-ECU connector.
<Less than 1 kΩ> Check the EPS-ECU connector, and repair if necessary. If the EPS-ECU connector is in good condition, replace the EPS-ECU.
 
STEP 13. Resistance measurement at joint connector (CAN1).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN1) terminal Nos.3 and 12
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN1) and C-126 intermediate connector.
<Less than 1 kΩ> Go to Step 14.
 
STEP 14. Resistance measurement at ASC-ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the ASC-ECU, and measure at the equipment side.
(2) Resistance between ASC-ECU connector terminal Nos.11 and 10
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN1) and the ASC-ECU connector.
<Less than 1 kΩ> Check the ASC-ECU connector, and repair if necessary. If the ASC-ECU connector is in good condition, replace the ASC-ECU.
 
STEP 15. Connector check: joint connector (CAN3).
cautionThe strand end of the twist wire should be within 10 cm (4 inches) from the connector. For details refer to .
When checking the joint connector, ensure that its wiring harness side and its short pins are not damaged.
Is the check result normal?
Go to Step 16.
Repair a defective connector or replace the joint connector.
 
STEP 16. Resistance measurement at joint connector (CAN3).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN3), and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN3) terminal Nos.11 and 22
OK: 120 ± 20 ohms
Is the check result normal?
<Within 120 ± 20 ohms> Go to Step 18.
: <Not within 120 ± 20 ohms> Go to Step 17.
 
STEP 17. Resistance measurement at ETACS-ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the ETACS-ECU, and measure at the equipment side.
(2) Resistance at ETACS-ECU connector terminal Nos.18 and 19
OK: 120 ± 20 ohms
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<Within 120 ± 20 ohms> Repair the wiring harness between joint connector (CAN3) and the ETACS-ECU connector.
<Not within 120 ± 20 ohms> Check the ETACS-ECU connector, and repair if necessary. If the ETACS-ECU connector is in good condition, replace the ETACS-ECU.
 
STEP 18. Resistance measurement at joint connector (CAN3).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN3), and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN3) terminal Nos.6 and 17
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 20.
<Less than 1 kΩ> Go to Step 19.
 
STEP 19. Resistance measurement at column switch connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the column switch assembly, and measure at the equipment side.
(2) Resistance at column switch connector terminal Nos.3 and 4
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN3) and the column switch connector.
<Less than 1 kΩ> Check the column switch connector, and repair if necessary. If the column switch connector is in good condition, replace the column switch assembly (steering wheel sensor).
 
STEP 20. Resistance measurement at joint connector (CAN3).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN3), and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN3) terminal Nos.4 and 15
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Go to Step 22.
<Less than 1 kΩ> Go to Step 21.
 
STEP 21. Resistance measurement at occupant classification-ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the occupant classification-ECU, and measure at the equipment side.
(2) Resistance at occupant classification-ECU connector terminal Nos.12 and 14
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN3) and the occupant classification-ECU connector.
<Less than 1 kΩ> Check the occupant classification-ECU connector, and repair if necessary. If the occupant classification-ECU connector is in good condition, replace the occupant classification-ECU.
 
STEP 22. Resistance measurement at joint connector (CAN3).
noteStep 22 and 23 are only for vehicles with FCM. On vehicles without it, go to Step 24.
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN3), and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN3) terminal Nos.7 and 18
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 24.
<Less than 1 kΩ> Go to Step 23.
 
STEP 23. Resistance measurement at FCM/LDW/AHB-ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the FCM/LDW/AHB-ECU, and measure at the equipment side.
(2) Resistance at FCM/LDW/AHB-ECU connector terminal Nos.2 and 8
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Check the intermediate connector, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between joint connector (CAN3) and the FCM/LDW/AHB-ECU connector.
<Less than 1 kΩ> Check the FCM/LDW/AHB-ECU connector, and repair if necessary. If the FCM/LDW/AHB-ECU connector is in good condition, replace the FCM/LDW/AHB-ECU.
 
STEP 24. Resistance measurement at joint connector (CAN3).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN3), and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN3) terminal Nos.8 and 19
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 26.
<Less than 1 kΩ> Go to Step 25.
 
STEP 25. Resistance measurement at SRS-ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the SRS-ECU, and measure at the equipment side.
(2) Resistance at SRS-ECU connector terminal Nos.30 and 29
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN3) and the SRS-ECU connector.
<Less than 1 kΩ> Check the SRS-ECU connector, and repair if necessary. If the SRS-ECU connector is in good condition, replace the SRS-ECU.
 
STEP 26. Resistance measurement at joint connector (CAN3).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN3), and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN3) terminal Nos.1 and 12
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 28.
<Less than 1 kΩ> Go to Step 27.
 
STEP 27. Resistance measurement at electric parking brake ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the electric parking brake ECU, and measure at the equipment side.
(2) Resistance at electric parking brake ECU connector terminal Nos.40 and 30
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN3) and the electric parking brake ECU.
<Less than 1 kΩ> Check the electric parking brake ECU connector, and repair if necessary. If the electric parking brake ECU connector is in good condition, replace the electric parking brake ECU.
 
STEP 28. Resistance measurement at joint connector (CAN3).
noteStep 28 and 29 are only for vehicles with Blind Spot Warning [BSW] (with Lane Change Assist) system. On vehicles without it, go to Step 30.
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN3), and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN3) terminal Nos.2 and 13
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 30.
<Less than 1 kΩ> Go to Step 29.
 
STEP 29. Resistance measurement at gateway-ECU connector.
cautionA digital multimeter should be used. For details refer to .
(1) Remove the gateway-ECU, and measure at the equipment side.
(2) Resistance at gateway-ECU connector terminal Nos.3 and 2
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN3) and the gateway-ECU.
<Less than 1 kΩ> Check the gateway-ECU connector, and repair if necessary. If the gateway-ECU connector is in good condition, replace the gateway-ECU.
 
STEP 30. Resistance measurement at joint connector (CAN3).
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect the joint connector (CAN3), and measure at the wiring harness side.
(2) Turn off the power supply mode of the electric motor switch.
(3)
cautionWhen measuring the resistance, disconnect the negative 12V starter battery terminal. For details refer to .
Ensure that the negative 12V starter battery terminal is disconnected.
(4) Resistance between joint connector (CAN3) terminal Nos.9 and 20
OK: 1 kΩ or more
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN2) and the C-126 intermediate connector.
<Less than 1 kΩ> Check the data link connector, and repair if necessary. If the data link connector is in good condition, repair the wiring harness between joint connector (CAN3) and the data link connector.