Inspection Procedure
1: M.U.T.-III cannot communicate with electric power steering system <ECU power supply
circuit system check>.
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COMMENTS ON TROUBLE SYMPTOM
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If the M.U.T.-III cannot communicate with the electric power steering system, the CAN
bus lines may be defective. If the electric power steering system does not operate, the EPS-ECU or
its power supply may be defective.
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- Malfunction of CAN bus line
- Defective harness wire(s) or connector(s)
- Short or open circuit between the EPS-ECU and the ETACS-ECU, the fusible
link or loose connector contact
- Open circuit between the body earth and the EPS-ECU or loose connector contact
- Malfunction of the ETACS-ECU
- Malfunction of the EPS-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics
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Use M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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Go to Step 2.
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Repair the CAN bus lines (Refer to GROUP 54C -
CAN Bus Diagnostics Table ).
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STEP 2. Voltage measurement at the EPS-ECU connector (IG1, +BB,
GND terminal)
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(1) Measure the EPS-ECU voltage without disconnecting the connector (by backprobing).
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(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Measure the voltage between the EPS-ECU connector (IG1 terminal) and the EPS-ECU
connector (GND terminal) or body earth. OK: Approximately system voltage
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(4)Measure the voltage between the EPS-ECU connector (+BB terminal) and the
EPS-ECU connector (GND terminal) or body earth. OK: Approximately system voltage
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Q.
Is the check result normal?
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Go to Step 5.
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Go to Step 3.
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STEP 3. Check of short to power supply, short to earth, and open circuit
in +BB line between fusible link and EPS-ECU connector
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Q.
Is the check result normal?
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Go to Step 4.
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Repair the fusible link, connector(s) or wiring harness.
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STEP 4. Check of short to power supply, short to earth, and open circuit
in IG1 line between EPS-ECU connector and ETACS-ECU connector
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Q.
Is the check result normal?
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Go to Step 5.
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Repair the connector(s) or wiring harness.
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STEP 5. Retest the system
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 -
How to Cope with Intermittent
Malfunction ).
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Replace the EPS-ECU (Refer to ).
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