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Inspection Procedure 7: When the brake auto hold switch is operated, the indicator light 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 light according to the request sent by the ASC-ECU.
 
 
COMMENTS ON TROUBLE SYMPTOM
This trouble symptom assumes that scan tool (M.U.T.-IIISE) CAN bus diagnosis result is OK and no DTC is set.
 
 
TROUBLESHOOTING HINTS
  • Damaged wiring harness or connector
    • Open or short to ground 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
 
 
DIAGNOSIS
Required Special Tools:
  • MB992006: Extra Fine Probe
STEP 1. Using scan tool (M.U.T.-IIISE), check the data list.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to Connect the Scan Tool (M.U.T.-IIISE) ."
(2) Check the following data list (Refer to ).
  • Item No.7: Auto hold switch
Is the check result normal?
Go to Step 5.
Go to Step 2.
 
STEP 2. Measure the resistance at the electric parking brake ECU connector and the electric parking brake switch connector.
(1) Disconnect the connector and measure at the wiring harness side.
(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 ohms or less).
(3) Measure the resistance between the electric parking brake ECU connector HSW terminal and body ground.
OK: No continuity.
Is the check result normal?
Go to Step 3.
The signal circuit may be open or short to ground. Repair the wiring harness wires or connectors between the electric parking brake switch and the electric parking brake ECU.
 
STEP 3. Check the brake auto hold switch.
Check the brake auto hold switch (Refer to ).
Is the check result normal?
Go to Step 4.
Replace the electric parking brake switch (Refer to ).
 
STEP 4. Retest the system
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Replace the electric parking brake ECU (Refer to ).
 
STEP 5. Measure the resistance at the electric parking brake ECU connector and the electric parking brake switch connector.
(1) Disconnect the connector and measure at the wiring harness side.
(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 ohms or less).
(3) Measure the resistance between the electric parking brake ECU connector HIND terminal and body ground.
OK: No continuity.
Is the check result normal?
Go to Step 6.
The signal circuit may be open or short to ground. Repair the wiring harness wires or connectors between the electric parking brake switch and the electric parking brake ECU.
 
STEP 6. Measure the voltage at the electric parking brake switch connector.
(1) Disconnect the electric parking brake switch connector and measure at the wiring harness side.
(2) Measure the voltage between the terminal No.5 and body ground.
OK: Battery voltage
Is the check result normal?
Go to Step 7.
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.
 
STEP 7. Check the brake auto hold Indicator.
Check the brake auto hold indicator (Refer to ).
Is the check result normal?
Go to Step 8.
Replace the electric parking brake switch (Refer to ).
 
STEP 8. Using scan tool (M.U.T.-IIISE), check the data list.
Check the following data list (Refer to ).
  • Item No.68: Auto hold switch indicator
Is the check result normal?
Go to Step 9.
Replace the hydraulic unit assembly (integrated with ASC-ECU) (Refer to GROUP 35C - Hydraulic Unit ).
 
STEP 9. Retest the system
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Replace the electric parking brake ECU (Refer to ).