Code No. C0047: Brake Vacuum Sensor Circuit <4N1>


OPERATION



  • The power voltage is supplied to the brake vacuum sensor connector power terminal from the AS&G-ECU connector terminal BVS5.
  • The sensor signal is inputted to the AS&G-ECU connector terminal BVS from the brake vacuum sensor connector output terminal.
  • The brake vacuum sensor connector earth terminal is earthed to the AS&G-ECU connector terminal BVSE.

FUNCTION



  • The brake vacuum sensor converts the vacuum pressure in the brake booster into a voltage and inputs the signal to the AS&G-ECU.
  • In response to the signal, the AS&G-ECU controls the AS&G system.

TROUBLE JUDGMENT


Check Condition
  • 2 seconds later after the ignition switch has been in "ON" position or the engine has started up.
Judgement Criterion
  • The brake vacuum sensor output voltage is less than 0.3 V for 2 seconds.


  • The brake vacuum sensor output voltage is more than 4.8 V for 2 seconds.

FAIL-SAFE AND BACKUP FUNCTION



  • In the normal operation, the auto stop is prohibited. If the malfunction is detected during the auto stop, carry out the forcible auto start.

PROBABLE CAUSES



  • Open/short circuit or harness damage in brake vacuum sensor circuit or loose connector contact
  • Failed brake vacuum sensor
  • Failed AS&G-ECU

DIAGNOSIS PROCEDURE

STEP 1. Perform voltage measurement at brake vacuum sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal AS&G-ECU BVS5 line and earth.
OK: 4.9 - 5.1 V

Q. Is the check result normal?
Go to Step 4.
Go to Step 2.

STEP 2. Check harness between C-64 AS&G-ECU connector terminal BVS5 and brake vacuum sensor connector terminal.

  • Check power supply line for open/short circuit.

Q. Is the check result normal?
Go to Step 3.
Repair the connector(s) or wiring harness.

STEP 3. M.U.T.-III diagnosis code

  • Reconfirmation of the diagnosis code.

Q. Is the diagnosis code set?
Replace the AS&G-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 4. Check of harness damage in BVS5 line between AS&G-ECU connector and brake vacuum sensor connector.

Q. Is the check result normal?
Go to Step 5.
Repair the connector(s) or wiring harness.

STEP 5. Check of short to earth, open circuit, and harness damage in BVS line between AS&G-ECU connector and brake vacuum sensor connector.

Q. Is the check result normal?
Go to Step 6.
Repair the connector(s) or wiring harness.

STEP 6. Check of short to earth, open circuit, and harness damage in BVSE line between AS&G-ECU connector and vacuum sensor connector terminal.

Q. Is the check result normal?
Go to Step 7.
Repair the connector(s) or wiring harness.

STEP 7. M.U.T.-III diagnosis code

  • Reconfirmation of the diagnosis code.

Q. Is the diagnosis code set?
Go to Step 8.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 8. Replace the brake vacuum sensor.

  • After replacing the brake vacuum sensor, reconfirm whether the diagnosis code is set.

Q. Is the diagnosis code set?
Replace the AS&G-ECU.
Check end.