Inspection Procedure
1: When the heated steering wheel switch is turned on, the heated steering wheel is not activated.
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COMMENTS ON TROUBLE SYMPTOM
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If the heated steering wheel cannot be not activated when the heated steering wheel switch
is turned on with the heated steering wheel deactivated, a component of the heated steering
wheel, the ETACS-ECU or the power supply lines to the heated steering wheel may be defective.
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- Malfunction of the ETACS-ECU
- Malfunction of heated steering wheel switch
- Malfunction of clock spring
- Malfunction of heated steering wheel relay
- Defective steering wheel (incorporating heated steering wheel-ECU and heater element)
- Defective harness wire(s) or connector(s)
- Short or open circuit between the ETACS-ECU and the heated steering wheel-ECU,
the fusible link or loose connector contact
- Open circuit between the body earth and the heated steering wheel relay or loose
connector contact
- Open circuit between the body earth and the heated steering wheel-ECU or loose connector
contact
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STEP 1. M.U.T.-III other system’s diagnosis code
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Check that the ETACS-ECU has not set a diagnosis code.
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Q.
Is the diagnosis code set?
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 Carry out the diagnosis code procedures (Refer to GROUP 54A - ETACS-ECU  ).
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 Go to Step 2.
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STEP 2. Check the heated steering wheel switch.
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Check the heated steering wheel switch (Refer to ).
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Q.
Is the check result normal?
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Go to Step 3.
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Replace the heated steering wheel switch (Refer to ).
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STEP 3. Check the clock spring.
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Check whether the clock spring is in good condition.
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Q.
Is the check result normal?
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Go to Step 4.
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Replace the clock spring.
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STEP 4. Check the heated steering wheel relay.
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Check the heated steering wheel relay (Refer to ).
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Q.
Is the check result normal?
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Go to Step 5.
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Replace the heated steering wheel relay.
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STEP 5. Voltage measurement at the heated steering wheel relay connector
(power supply line).
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(1)Removal the heated steering wheel relay, and measure at the wiring harness side.
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(2)Set the ignition switch or engine switch to ON.
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(3)Measure the voltage in power supply and IG line between the heated steering wheel
relay connector and the body earth.
OK: Approximately system voltage
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Q.
Is the check result normal?
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Go to Step 6.
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Repair the connector(s) or wiring harness.
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STEP 6. Resistance measurement at the heated steering wheel relay
connector (earth line).
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(1)Removal the heated steering wheel relay, and measure at the wiring harness side.
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(2)Resistance in earth line between the heated steering wheel relay connector 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 7.
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Repair the connector(s) or wiring harness.
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STEP 7. Voltage measurement at the heated steering wheel-ECU connector
(IG terminal)
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(1) Measure the heated steering wheel-ECU voltage with disconnecting the connector.
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(2)Set the ignition switch or engine switch to ON.
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(3)Measure the voltage between the heated steering wheel-ECU connector (IG terminal)
and the body earth.
OK: Approximately system voltage
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Q.
Is the check result normal?
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Go to Step 10.
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Go to Step 8.
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STEP 8. Check the fusible link and fuse in the relay box.
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Q.
Is the check result normal?
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Go to Step 9.
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Repair the fusible link and fuse in the relay box.
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STEP 9. Check of short to power supply, short to earth, and open circuit
in IG line between fusible link No.3 and heated steering wheel-ECU (IG terminal) connector
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Q.
Is the check result normal?
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Intermittent malfunction.
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Repair the connector(s) or wiring harness.
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STEP 10. Voltage measurement at the heated steering wheel-ECU connector
(SW terminal)
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(1) Measure the heated steering wheel-ECU voltage with disconnecting the connector.
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(2)Set the ignition switch or engine switch to ON.
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(3)Set the heated steering wheel switch to ON.
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(4)Measure the voltage between the heated steering wheel-ECU connector (SW terminal)
and the body earth.
OK: Approximately system voltage
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Q.
Is the check result normal?
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Go to Step 12.
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Go to Step 11.
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STEP 11. Check of short to power supply, short to earth, and open
circuit in SW line between heated steering wheel switch connector and heated steering wheel-ECU connector
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Q.
Is the check result normal?
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Intermittent malfunction.
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Repair the connector(s) or wiring harness.
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STEP 12. Resistance measurement at the heated steering wheel-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 heated steering wheel-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 14.
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Go to Step 13.
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STEP 13. Check of open circuit in GND line between heated steering
wheel-ECU connector and body earth.
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Q.
Is the check result normal?
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Intermittent malfunction.
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Repair the connector(s) or wiring harness.
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STEP 14. Retest the system
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Q.
Is the check result normal?
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Intermittent malfunction.
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Replace the heated steering wheel ECU (Refer to ).
Then go to Step 15.
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STEP 15. Retest the system
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Q.
Is the check result normal?
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This diagnosis is complete.
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Replace the steering wheel (Refer to ).
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