Diagnosis Item 28: Diagnose when the M.U.T.-III cannot receive the data sent by ACC-ECU. <Vehicles with ACC>
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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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FUNCTION
The diagnostic result demonstrates that "the M.U.T.-III cannot receive the sent data from the ACC-ECU" when the M.U.T.-III checks the periodically sent data from each ECU and cannot receive the ACC-ECU data only.
TROUBLE JUDGEMENT CONDITIONS
M.U.T.-III judges the trouble when the periodically sent data from ACC-ECU cannot be received.
PROBABLE CAUSES
- Damaged harness wires and connectors
- Power supply circuit malfunction of the ACC-ECU
- Malfunction of the ACC-ECU
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STEP 1. Connector check: joint connector (CAN2) and ACC-ECU connector
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The strand end of the twist wire should be within 10 cm from the connector.
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When checking the joint connector, ensure that its wiring harness side and its short pins are not damaged.
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Q.
Is the check result normal?
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 Go to Step 2.
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 Repair the defective connector. Replace the joint connector as necessary.
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STEP 2. Resistance measurement at joint connector (CAN2) and ACC-ECU connector.
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A digital multimeter should be used.
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The test wiring harness should be used.
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(1)Disconnect joint connector (CAN2) and the ACC-ECU connector, and measure at the wiring harness side.
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(2)Turn the ignition switch to the LOCK (OFF) position.
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(3)
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When measuring the resistance, disconnect the negative battery terminal.
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Ensure that the negative battery terminal is disconnected.
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(4)Continuity between joint connector (CAN2) terminal No.9 and ACC-ECU connector terminal No.2
OK: Continuity (2 Ω or less)
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(5)Continuity between joint connector (CAN2) terminal No.20 and ACC-ECU connector terminal No.7
OK: Continuity (2 Ω or less)
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Strictly observe the specified wiring harness repair procedure.
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Q.
Is the check result normal?
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<All the resistances measure 2 Ω or less> Go to Step 3.
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NO : <Either or all of the resistances measure more than 2 Ω> Repair the wiring harness between joint connector (CAN2) and the ACC-ECU connector.
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STEP 3. Resistance measurement at ACC-ECU connector.
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A digital multimeter should be used.
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(1)Remove the ACC-ECU, and measure at the equipment side.
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(2)Resistance between ACC-ECU connector terminal Nos.2 and 7
OK: 1 kΩ or more
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Q.
Is the check result normal?
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Power supply to the ACC-ECU may be suspected. Diagnose the ACC. Refer to GROUP 17 - Troubleshooting.
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Replace the ACC-ECU.
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