Diagnosis Item 21: Diagnose when the M.U.T.-III cannot receive the data sent by engine-ECU. <Vehicles for LHD>
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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 engine-ECU" when the M.U.T.-III checks the periodically sent data from each ECU and cannot receive the engine-ECU data only.
TROUBLE JUDGEMENT CONDITIONS
M.U.T.-III judges the trouble when the periodically sent data from engine-ECU cannot be received.
PROBABLE CAUSES
- Damaged harness wires and connectors
- Power supply circuit malfunction of the engine-ECU
- Malfunction of the engine-ECU
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STEP 1. Connector check: joint connector (CAN1), joint connector (CAN3), D-26 intermediate connector and engine-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 (CAN1) and D-26 intermediate 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 joint connector (CAN1) and D-26 intermediate 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 (CAN1) terminal No.10 and D-26 intermediate connector terminal No.19.
OK: Continuity (2 Ω or less)
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(5)Continuity between joint connector (CAN1) terminal No.21 and D-26 intermediate connector terminal No.18.
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 (CAN1) and D-26 intermediate connector.
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STEP 3. Resistance measurement at D-26 intermediate connector and joint connector (CAN3).
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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 D-26 intermediate connector and joint connector (CAN3), 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 D-26 intermediate connector terminal No.19 and joint connector (CAN3) terminal No.10.
OK: Continuity (2 Ω or less)
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(5)Continuity between D-26 intermediate connector terminal No.18 and joint connector (CAN3) terminal No.21.
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 4
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NO : <Either or all of the resistances measure more than 2 Ω> Repair the wiring harness between D-26 intermediate connector and joint connector (CAN3).
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STEP 4. Resistance measurement at joint connector (CAN3) and engine-ECU connector.
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| caution |
A digital multimeter should be used.
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The test wiring harness should be used.
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(1)Disconnect the joint connector (CAN3) and the engine-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 (CAN3) terminal No.11 and engine-ECU connector terminal No.101 <6B31>, 108 <4N15, 4D56>.
OK: Continuity (2 Ω or less)
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(5)Continuity between joint connector (CAN3) terminal No.22 and engine-ECU connector terminal No.102 <6B31>, 109 <4N15, 4D56>.
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 5
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NO : <Either or all of the resistances measure more than 2 Ω> Repair the wiring harness between joint connector (CAN3) and the engine-ECU.
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STEP 5. Resistance measurement at engine-ECU connector.
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A digital multimeter should be used.
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(1)Remove the engine-ECU, and measure at the equipment side.
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(2)Resistance between engine-ECU connector terminal Nos.101 and 102 <6B31> or 108 and 109 <4N15, 4D56>.
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> Power supply to the engine-ECU may be suspected. Diagnose the fuel system (Refer to GROUP 13B - Troubleshooting <6B31>, GROUP 13C - Troubleshooting <4N15> or GROUP 13E - Troubleshooting  <4D56>).
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<Not within 120 ± 20 Ω> Replace the engine-ECU (Refer to GROUP 13B - Engine-ECU <6B31>, GROUP 13C - Engine-ECU <4N15> or GROUP 13E - Engine-ECU <4D56>).
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