Inspection Procedure
7: When the brake auto hold switch is operated, the indicator lamp on the switch is not switched.
OPERATION
The electric parking brake ECU provides the ASC-ECU with the brake auto hold switch ON/OFF information.
The electric parking brake ECU activates or deactivates the brake auto hold switch indicator
lamp according to the request sent by the ASC-ECU.
COMMENTS ON TROUBLE SYMPTOM
This trouble symptom assumes that M.U.T.-III CAN bus diagnosis result is OK and no diagnosis
code is et.
PROBABLE CAUSES
- Damaged wiring harness or connector
- Open or short to earth in the wires between the electric parking brake switch
and the electric parking brake ECU, or high resistance in a connector
- Malfunction of the electric parking brake switch (brake auto hold switch)
- The switch stuck on or off, or poor contacts
- The brake auto hold switch indicator fails
- Malfunction of the ASC-ECU
- Malfunction of the electric parking brake ECU
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STEP 1. M.U.T.-III data list
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Check the following data list (Refer to  ).
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- Item No.7: Auto hold switch
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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 2.
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STEP 2. Measure the resistance at the electric parking brake ECU connector
and the electric parking brake switch connector.
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(1)Disconnect the connector and measure at the wiring harness side.
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(2)Measure the resistance between the electric parking brake ECU connector HSW terminal
and the electric parking brake switch connector terminal No.8.
OK: Continuity exists (2 Ω or less).
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(3)Measure the resistance between the electric parking brake ECU connector HSW terminal
and body earth.
OK: No continuity.
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Q.
Is the check result normal?
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Go to Step 3.
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The signal circuit may be open or short to earth. Repair the wiring harness wires
or connectors between the electric parking brake switch and the electric parking brake ECU.
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STEP 3. Check the brake auto hold switch.
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Check the brake auto hold switch (Refer to ).
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Q.
Is the check result normal?
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Go to Step 4.
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Replace the electric parking brake switch (Refer to ).
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STEP 4. 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 electric parking brake ECU (Refer to ).
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STEP 5. Measure the resistance at the electric parking brake ECU connector
and the electric parking brake switch connector.
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(1)Disconnect the connector and measure at the wiring harness side.
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(2)Measure the resistance between the electric parking brake ECU connector HIND terminal
and the electric parking brake switch connector terminal No.11.
OK: Continuity exists (2 Ω or less).
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(3)Measure the resistance between the electric parking brake ECU connector HIND terminal
and body earth.
OK: No continuity.
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Q.
Is the check result normal?
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Go to Step 6.
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The signal circuit may be open or short to earth. Repair the wiring harness wires
or connectors between the electric parking brake switch and the electric parking brake ECU.
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STEP 6. Measure the voltage at the electric parking brake switch connector.
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(1)Disconnect the electric parking brake switch connector and measure at the wiring
harness side.
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(2)Measure the voltage between the terminal No.5 and body earth.
OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 7.
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The power supply circuit may be open. Repair the wiring harness wires or connectors
between the electric parking brake switch connector and the fusible link.
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STEP 7. Check the brake auto hold Indicator.
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Check the brake auto hold indicator (Refer to ).
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Q.
Is the check result normal?
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Go to Step 8.
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Replace the electric parking brake switch (Refer to ).
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STEP 8. M.U.T.-III data list
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Check the following data list (Refer to ).
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- Item No.68: Auto hold switch indicator
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Q.
Is the check result normal?
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Go to Step 9.
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Replace the hydraulic unit assembly (integrated with ASC-ECU) (Refer to GROUP
35C - Hydraulic Unit).
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STEP 9. 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 electric parking brake ECU (Refer to ).
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