P0555 – Brake Vacuum Sensor System Vehicles with AS&G system MMC Colt



OPERATION

  • A power voltage of 5 V is applied to the brake vacuum sensor power terminal (terminal No. 3) from the engine-ECU (terminal No. 127) and earthed to the engine-ECU (terminal No. 130) from the brake vacuum sensor (terminal No. 2).
  • The sensor signal is inputted to the engine-ECU (terminal No. 128) from the brake vacuum sensor output terminal (terminal No. 1).

  • FUNCTION

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

  • TROUBLE JUDGMENT

  • 2 seconds later after the ignition switch has been in “ON” position or the engine has started up.
  • The brake vacuum sensor output voltage is 4.5 V or more for 2 seconds.
  • The brake vacuum sensor output voltage is 0.2 V or less for 2 seconds.

  • PROBABLE CAUSES

  • Failed brake vacuum sensor
  • Open or shorted brake vacuum sensor circuit, harness damage, or connector damage
  • Failed engine-ECU

  • DIAGNOSIS PROCEDURE

    STEP 1. M.U.T.-III data list

  • Item No. 161: Brake vacuum sensor
  • Q. Is the check result normal?

    STEP 2. Connector check: A-38 brake vacuum sensor connector

    Q. Is the check result normal?

    STEP 3. Perform voltage measurement at A-38 brake vacuum sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 3 and earth.
  • Q. Is the check result normal?

    STEP 4. Connector check: A-09 engine-ECU connector

    Q. Is the check result normal?

    STEP 5. Check harness between A-38 (terminal No. 3) brake vacuum sensor connector and A-09 (terminal No. 127) engine-ECU connector.

  • Check power supply line for open/short circuit.
  • Q. Is the check result normal?

    STEP 6. M.U.T.-III data list

  • Item No. 161: Brake vacuum sensor
  • Q. Is the check result normal?

    STEP 7. Perform resistance measurement at A-38 brake vacuum sensor connector.

  • Disconnect connector, and measure at harness side.
  • Resistance between terminal No. 2 and earth.
  • Q. Is the check result normal?

    STEP 8. Connector check: A-09 engine-ECU connector

    Q. Is the check result normal?

    STEP 9. Check harness between A-38 (terminal No. 2) brake vacuum sensor connector and A-09 (terminal No. 130) engine-ECU connector.

  • Check earthing line for open circuit and damage.
  • Q. Is the check result normal?

    STEP 10. Connector check: A-09 engine-ECU connector

    Q. Is the check result normal?

    STEP 11. Check harness between A-38 (terminal No. 3) brake vacuum sensor connector and A-09 (terminal No. 127) engine-ECU connector.

  • Check power supply line for damage.
  • Q. Is the check result normal?

    STEP 12. Perform voltage measurement at A-38 brake vacuum sensor connector.

  • Use special tool test harness (MB991658) to connect connector, and measure at pick-up harness.
  • Engine: Warming up, idle
  • Voltage between terminal No. 1 and earth.
  • Q. Is the check result normal?

    STEP 13. Check harness between A-38 (terminal No. 1) brake vacuum sensor connector and A-09 (terminal No. 128) engine-ECU connector.

  • Check output line for short circuit.
  • Q. Is the check result normal?

    STEP 14. Perform voltage measurement at A-09 engine-ECU connector.

  • Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB991987), and then measure the voltage on the check connector.
  • Engine: Warming up, idle
  • Voltage between terminal No. 128 and earth.
  • Q. Is the check result normal?

    STEP 15. Connector check: A-09 engine-ECU connector

    Q. Is the check result normal?

  • Check output line for open circuit and damage.
  • Author: admin