Inspection Procedure 2: Electric power steering system warning display illuminates but diagnosis code is not set.
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COMMENTS ON TROUBLE SYMPTOM
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The CAN bus lines may be defective. If the electric power steering system does not operate, the combination meter or the EPS-ECU 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 combination meter
- 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. Diagnosis code recheck after resetting CAN bus lines
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
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(3)Check if the diagnosis code is set.
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Q.
Is diagnosis code C1541 set?
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Go to Step 3.
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This diagnosis is complete.
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STEP 3. Check by M.U.T.-III "Special Function"
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Using M.U.T.-III, select "Test" from the special function of the combination meter. Execute the following item to check the liquid crystal display. (Refer to GROUP 54A -
Combination Meter.)
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Q.
Is the check result normal?
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Go to Step 4.
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Replace the combination meter (Refer to GROUP 54A -
Combination Meter).
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STEP 4. Voltage measurement at the EPS-ECU connector (+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 (+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 7.
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Go to Step 5.
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STEP 5. Check the fusible link.
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Q.
Is the check result normal?
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Go to Step 6.
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Repair the fusible link.
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STEP 6. 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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Prior to the wiring harness inspection, check intermediate connector and repair if necessary.
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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 Malfunctions).
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Repair the fusible link, connector(s) or wiring harness.
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STEP 7. Voltage measurement at the EPS-ECU connector (IG1, 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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Q.
Is the check result normal?
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Go to Step 9.
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Go to Step 8.
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STEP 8. 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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Prior to the wiring harness inspection, check joint connector and repair if necessary.
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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 Malfunctions).
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Repair the connector(s) or wiring harness.
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STEP 9. Resistance measurement at the EPS-ECU connector (GND terminal).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Resistance between the EPS-ECU connector (GND terminal) and body earth
OK: Continuity exists (2 Ω
or less)
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Q.
Is the check result normal?
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Go to Step 11.
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Go to Step 10.
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STEP 10. Check of open circuit in GND line between EPS-ECU connector and body earth.
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Prior to the wiring harness inspection, check intermediate connector and repair if necessary.
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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 Malfunctions).
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Repair the connector(s) or wiring harness.
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STEP 11. 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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