Diagnosis
Item 5: Communication with no ECUs is possible (SUB). <Vehicles with Automatic A/C>
| 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 sub bus line (short to earth or power
supply, wire short to one another)
- Malfunction in the ECUs which are interconnected via CAN sub bus line (internal error)
- Malfunction (open circuit) of wiring harness, connector (s) between the diagnosis
connector and joint connector(s)
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STEP 1. Check the CAN bus lines for short to power supply.
Voltage measurement at gateway-ECU connector.
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| caution |
A digital multimeter should be used. For details refer to  .
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| caution |
The test wiring harness should be used. For details refer
to .
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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 gateway-ECU connector terminal No.6 (CAN_H) and body earth.
OK: Less than 4.0 V
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(3)Voltage between gateway-ECU connector terminal No.5 (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?
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YES <Voltage is less than 4.0 V in both CAN_H and CAN_L> : Go to Step 2.
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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 bus line
(SUB)" (Refer to ).
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STEP 2. Check the CAN bus lines for short to earth. Resistance measurement
at gateway-ECU connector.
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| caution |
A digital multimeter should be used. For details refer to .
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| caution |
The test wiring harness should be used. For details refer
to .
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(1)Turn the ignition switch to the "LOCK" (OFF) position.
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(2)
| caution |
When measuring the resistance, disconnect the negative battery
terminal. For details refer to .
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Ensure that the negative battery terminal is disconnected.
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(3)Resistance between gateway-ECU connector terminal No.6 (CAN_H) and body
earth.
OK: 1 kΩ or more
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(4)Resistance between gateway-ECU connector terminal No.5 (CAN_L) and body
earth.
OK: 1 kΩ or more
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Q.
Is the check result normal?
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YES <Resistance value is 1 kΩ or more in both CAN_H and CAN_L> : Go to Step 3.
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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 bus line (SUB)"
(Refer to ).
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STEP 3. Check the CAN bus lines for short to each other. Resistance
measurement at gateway-ECU connector.
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| caution |
A digital multimeter should be used. For details refer to .
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| caution |
The test wiring harness should be used. For details refer
to .
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(1)Turn the ignition switch to the "LOCK" (OFF) position.
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(2)
| caution |
When measuring the resistance, disconnect the negative battery
terminal. For details refer to .
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Ensure that the negative battery terminal is disconnected.
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(3)Resistance between gateway-ECU connector terminal Nos.5 and 6.
OK: 120 ± 20 Ω
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Q.
Is the check result normal?
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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 ).
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NO <Resistance value is less than 120 ± 20 Ω> : Perform diagnosis Item 8 "Diagnose shorts between CAN_H and L lines (SUB)"
(Refer to ).
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NO <Resistance value is 1 kΩ or more> : Check the wires between gateway-ECU connector and joint connector (CAN4) for open
circuit, and check the terminal resistors in the A/C-ECU and the gateway-ECU for open circuit.
Then repair or replace if necessary.
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