Diagnosis Item 5: Communication with no ECUs is possible (CAN-C-Mid).


caution When servicing a CAN bus line, earth 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.

TROUBLESHOOTING HINTS



  • Malfunction in CAN-C-Mid (short to earth or power supply, wire short to one another)
  • Malfunction in the ECUs which are interconnected via CAN-C-Mid (internal error)
  • Malfunction (open circuit) of wiring harness, connector (s) between the ETACS-ECU and joint connector(s)

DIAGNOSIS PROCEDURE

STEP 1. Check the CAN-C-Mid for short to power supply. Voltage measurement at ETACS-ECU connector by backprobing.
caution A digital multimeter should be used. For details refer to .
caution The test wiring harness should be used. For details refer to .
(1)Connect the negative battery terminal, and turn the ignition switch to the ON position.
(2)Voltage between ETACS-ECU connector terminal No.17 (CAN_H) and body earth by backprobing
OK: Less than 4.0 V
(3)Voltage between ETACS-ECU connector terminal No.16 (CAN_L) and body earth by backprobing
OK: Less than 4.0 V

Q. Is the check result normal?
YES <Voltage is less than 4.0 V in both CAN_H and CAN_L> : Go to Step 2.
NO <Voltage is 4.0 V or more in either CAN_H or CAN_L> : Perform diagnosis item 6 "Diagnose shorts in the power supply to CAN-C-Mid". Refer to .

STEP 2. Check the CAN-C-Mid for short to earth. Resistance measurement at ETACS-ECU connector by backprobing.
caution A digital multimeter should be used. For details refer to .
caution The test wiring harness should be used. For details refer to .
(1)Turn the ignition switch to the LOCK (OFF) position.
(2)
caution When measuring the resistance, disconnect the negative battery terminal. For details refer to .
Ensure that the negative battery terminal is disconnected.
(3)Resistance between ETACS-ECU connector terminal No.17 (CAN_H) and body earth by backprobing
OK: 1 kΩ or more
(4)Resistance between ETACS-ECU connector terminal No.16 (CAN_L) and body earth by backprobing
OK: 1 kΩ or more

Q. Is the check result normal?
YES <Resistance value is 1 kΩ or more in both CAN_H and CAN_L> : Go to Step 3.
NO <Resistance value is less than 1 kΩ in either CAN_H or CAN_L> : Perform diagnosis item 7 "Diagnose shorts in the earth to CAN-C-Mid". Refer to .

STEP 3. Check the CAN-C-Mid for short to each other. Resistance measurement at ETACS-ECU connector by backprobing.
caution A digital multimeter should be used. For details refer to .
caution The test wiring harness should be used. For details refer to .
(1)Turn the ignition switch to the LOCK (OFF) position.
(2)
caution When measuring the resistance, disconnect the negative battery terminal. For details refer to .
Ensure that the negative battery terminal is disconnected.
(3)Resistance between ETACS-ECU connector terminal Nos.16 and 17 by backprobing
OK: 60 ± 10 Ω

Q. Is the check result normal?
YES : The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
NO <Resistance value is less than 60 ± 10 Ω> : Perform diagnosis Item 8 "Diagnose shorts between CAN_H and L lines (CAN-C-Mid)". Refer to .
NO <Resistance value is 1 kΩ or more> : Check the wires between ETACS-ECU connector and joint connector (CAN5) for open circuit, and check the terminal resistors in the combination meter and the ETACS-ECU for open circuit. Then repair or replace if necessary.