Code No. C0047: Brake Vacuum Sensor Circuit

OPERATION

The power voltage is supplied to the brake vacuum sensor (terminal No. 3) from the AS&G-ECU (terminal No. 7).
The sensor signal is inputted to the AS&G-ECU (terminal No. 9) from the brake vacuum sensor (terminal No. 2).
The brake vacuum sensor (terminal No. 1) is earthed to the AS&G-ECU (terminal No. 2).

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.

or

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. Connector check: A-78 brake vacuum sensor connector

Q. Is the check result normal?

	Go to Step 2 .

	Repair or replace the connector.

STEP 2. Perform voltage measurement at A-78 brake vacuum sensor connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 3 and earth.

OK: 4.9 - 5.1 V

Q. Is the check result normal?

	Go to Step 6 .

	Go to Step 3 .

STEP 3. Connector check: C-45 AS&G-ECU connector

Q. Is the check result normal?

	Go to Step 4 .

	Repair or replace the connector.

STEP 4. Check harness between C-45 (terminal No. 7) AS&G-ECU connector and A-78 (terminal No. 3) brake vacuum sensor connector.

Check power supply line for open/short circuit.

Q. Is the check result normal?

	Go to Step 5 .

	Repair the damaged harness wire.

STEP 5. 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 6. Connector check: C-45 AS&G-ECU connector

Q. Is the check result normal?

	Go to Step 7 .

	Repair or replace the connector.

STEP 7. Check harness between C-45 (terminal No. 7) AS&G-ECU connector and A-78 (terminal No. 3) brake vacuum sensor connector.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 8 .

	Repair the damaged harness wire.

STEP 8. Check harness between C-45 (terminal No. 9) AS&G-ECU connector and A-78 (terminal No. 2) brake vacuum sensor connector.

Check output line for open/short circuit and damage.

Q. Is the check result normal?

	Go to Step 9 .

	Repair the damaged harness wire.

STEP 9. Check harness between C-45 (terminal No. 2) AS&G-ECU connector and A-78 (terminal No. 1) brake vacuum sensor connector.

Check earthing line for open/short circuit and damage.

Q. Is the check result normal?

	Go to Step 10 .

	Repair the damaged harness wire.

STEP 10. M.U.T.-III diagnosis code

Reconfirmation of the diagnosis code.

Q. Is the diagnosis code set?

	Go to Step 11 .

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 11. 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.