Diagnosis Item 8: Diagnose shorts between CAN_H and L lines (GW-CAN-C). <Vehicles with Blind Spot Warning [BSW] (with Lane Change Assist) system>
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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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TROUBLE JUDGEMENT
When all of the following conditions are met, the M.U.T.-III determines that a short circuit is present between CAN_L and CAN_H lines.
- The M.U.T.-III cannot receive the periodic transmission data from any ECUs.
- The voltage between CAN-C (CAN_L and CAN_H lines) is 1.0 V or more, 4.0 V or less.
- The resistance at CAN-C (CAN_L and CAN_H lines) is 2 Ω or less.
TROUBLESHOOTING HINTS
- Malfunction of the wiring harness
- Malfunction of the gateway-ECU
- Malfunction of the BSW-ECU (master)
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STEP 1. Check the GW-CAN-C. Resistance measurement at gateway-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 the gateway-ECU connector and the BSW-ECU (master) connector, and measure at the wiring harness side.
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(2)
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When measuring the resistance, disconnect the negative auxiliary battery terminal.
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Ensure that the negative battery terminal is disconnected.
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(3)Resistance between the gateway-ECU connector terminal No.6 (CAN_H) and No.5 (CAN_L).
OK: 1 kΩ or more
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Q.
Is the check result normal?
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 <1 kΩ or more> Go to Step 2.
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 <Less than 1 kΩ > Repair intermediate connectors C-25 and G-36, or the wiring harness between the gateway-ECU connector and the BSW-ECU (master) connector.
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STEP 2. Resistance measurement at BSW-ECU (master) connector.
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A digital multimeter should be used.
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(1)Remove the BSW-ECU (master), and measure at the equipment side.
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(2)Resistance between the BSW-ECU (master) connector terminal Nos.4 and 9.
OK: 120 ± 20 Ω
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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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<Within 120 ± 20 Ω> Go to Step 3.
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<Not within 120 ± 20 Ω> Check the BSW-ECU (master) connector, and repair if necessary. If the BSW-ECU (master) connector is in good condition, replace the BSW-ECU (master).
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STEP 3. Resistance measurement at gateway-ECU connector.
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A digital multimeter should be used.
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(1)Remove the gateway-ECU, and measure at the equipment side.
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(2)Resistance between the gateway-ECU connector terminal Nos.5 and 6
OK: 120 ± 20 Ω
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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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<Within 120 ± 20 Ω> 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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<Not within 120 ± 20 Ω> Check the gateway-ECU connector, and repair if necessary. If the gateway-ECU connector is in good condition, replace the gateway-ECU.
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