Inspection Procedure
2: Electric power steering system warning display illuminates but diagnosis code is not set.
COMMENTS ON TROUBLE SYMPTOM
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.
PROBABLE CAUSES
- Malfunction of CAN bus line
- Defective harness wire(s) or connector(s)
- Short or open circuit between the EPS-ECU and the junction block, the fusible
link or loose connector contact
- Open circuit between the body earth and the EPS-ECU or loose connector contact
- 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. Wiring harness check
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(1)Check the wiring harness between the junction block connector terminal and the
fusible link for damage or other problem.
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(2)Check the wiring harness between the EPS-ECU connector terminal IG1 and the junction
block connector terminal for damage or other problem.
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(3)Check the wiring harness between the EPS-ECU connector terminal +BB and
the junction block connector terminal for damage or other problem.
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(4)Check the wiring harness between the EPS-ECU connector terminal GND and the body
earth point for damage or other problem.
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Q.
Is the check result normal?
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Go to step 3.
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Repair the defective connector(s) or terminal(s), or repair the defective wiring
harness.
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STEP 3. Voltage measurement at the junction block connector
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(1)Measure the junction block 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 junction block connector terminals.
OK: Approximately system voltage
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Q.
Is the check result normal?
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Go to Step 4.
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Check the fusible link or the junction block and repair if necessary.
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STEP 4. Voltage measurement at the EPS-ECU connector
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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 terminal IG1 and GND.
OK: Approximately system voltage
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(4)Measure the voltage between the EPS-ECU connector terminals +BB and GND.
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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Check the fusible link or the junction block and repair if necessary.
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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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