54C-DIAGNOSTICS ITEM 1

Diagnostic Item 1: Communication with no ECUs is possible.

caution

When 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.

TROUBLESHOOTING HINTS

Malfunction in CAN bus line (short to ground or power supply, wire short to one another)
Malfunction in the ECUs which are interconnected via CAN bus line (internal error)
Malfunction (open circuit) of wiring harness, connector (s) between the data link connector and joint connector(s)

DIAGNOSIS

STEP 1. Check the CAN bus lines for short to power supply. Voltage measurement at data link connector.

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 data link connector terminal No.6 (CAN_H) and body ground

OK: Less than 4.0 V

(3) Voltage between data link connector terminal No.14 (CAN_L) and body ground

OK: Less than 4.0 V

(4) Disconnect the negative battery terminal.

Is the check result normal?

<Voltage is less than 4.0 V in both CAN_H and CAN_L> : Go to Step 2

<Voltage is 4.0 V or more in either CAN_H or CAN_L> : Perform diagnosis item 2 "Diagnose shorts in the power supply to CAN bus line". Refer to

STEP 2. Check the CAN bus lines for short to ground. Resistance measurement at data link connector.

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 data link connector terminal No.6 (CAN_H) and body ground

OK: 1 kΩ or more

(4) Resistance between data link connector terminal No.14 (CAN_L) and body ground

OK: 1 kΩ or more

Is the check result normal?

<Resistance value is 1 kΩ or more in both CAN_H and CAN_L> : Go to Step 3

<Resistance value is less than 1 kΩ in either CAN_H or CAN_L> : Perform diagnosis item 3 "Diagnose shorts in the ground to CAN bus line". Refer to

STEP 3. Check the CAN bus lines for short to each other. Resistance measurement at data link connector.

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 data link connector terminal Nos.6 and 14

OK: 60 ± 10 Ω

Is the check result normal?

The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction

<Resistance value is less than 60 ± 10 Ω> : Perform diagnosis Item 4 "Diagnose shorts between CAN_H and L lines". Refer to

<Resistance value is 1 kΩ or more> : Check the wires between data link connector and joint connector (CAN1) for open circuit, and check the terminal resistors in the engine control module and the ETACS-ECU for open circuit. Then repair or replace if necessary.