Diagnosis Item
1: Communication with no ECUs is possible.
| 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.
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TROUBLESHOOTING HINTS
- Malfunction in CAN bus line (short to earth 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 diagnosis
connector and joint connector(s)
DIAGNOSIS PROCEDURE
STEP 1. Check the CAN bus lines for short to power supply.
Voltage measurement at diagnosis connector.
| caution |
- A digital multimeter should
be used. For details refer to service precautions.
- The test wiring harness should be used. For details refer to service precautions.
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(1)Connect the negative battery terminal, and turn the ignition switch to the "ON"
position.
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(2)Voltage between diagnosis connector terminal No.6 (CAN_H) and body earth
OK: Less than 4.0 V
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(3)Voltage between diagnosis connector terminal No.14 (CAN_L) and body earth
OK: Less than 4.0 V
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(4)Disconnect the negative battery terminal.
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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 2 "Diagnose shorts in the power supply to CAN bus line". Refer
to 
<LHD> or <RHD>.
STEP 2. Check the CAN bus lines for short to earth. Resistance measurement
at diagnosis connector.
| caution |
- A digital multimeter should
be used. For details refer to service precautions.
- The test wiring harness should be used. For details refer to service precautions.
- When measuring the resistance, disconnect the negative battery terminal. For details
refer to service precautions.
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(1)Turn the ignition switch to the "LOCK" (OFF) position.
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(2)Ensure that the negative battery terminal is disconnected.
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(3)Resistance between diagnosis connector terminal No.6 (CAN_H) and body
earth
OK: 1 kΩ or more
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(4)Resistance between diagnosis connector terminal No.14 (CAN_L) and body
earth
OK: 1 kΩ or more
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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 3 "Diagnose shorts in the earth to CAN bus line". Refer
to <LHD> or <RHD>.
STEP 3. Check the CAN bus lines for short to each other. Resistance
measurement at diagnosis connector.
| caution |
- A digital multimeter should
be used. For details refer to service precautions.
- The test wiring harness should be used. For details refer to service precautions.
- When measuring the resistance, disconnect the negative battery terminal. For details
refer to service precautions.
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(1)Turn the ignition switch to the "LOCK" (OFF) position.
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(2)Ensure that the negative battery terminal is disconnected.
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(3)Resistance between diagnosis connector terminal Nos.6 and 14
OK: 60 ± 10 Ω
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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 4 "Diagnose shorts between CAN_H and L lines".
Refer to <LHD> or <RHD>.
NO <Resistance value is 1 kΩ or more> : Check the wires between diagnosis connector and joint connector (CAN1) for open
circuit, and check the terminal resistors in the engine-ECU and the ETACS-ECU for open circuit. Then
repair or replace if necessary.