P0546 – No. 1 exhaust gas temperature sensor Circuit High Input Euro5b MMC L200 IV



OPERATION

  • A power voltage of 5 V is applied to the No. 1 exhaust gas temperature sensor output terminal (terminal No. 1) from the engine-ECU (terminal No. 58).
  • The power voltage is earthed to the engine-ECU (terminal No. 82) from the No. 1 exhaust gas temperature sensor (terminal No. 2).

  • FUNCTION

  • The No. 1 exhaust gas temperature sensor converts the exhaust gas temperature into a voltage and inputs the voltage signal to the engine-ECU.
  • Engine-ECU uses this voltage for DPF regeneration control.
  • The No. 1 exhaust gas temperature sensor is a kind of resistor, which has characteristics to reduce its resistance as the exhaust gas temperature rises. Therefore, the sensor output voltage varies with the exhaust gas temperature, and becomes lower as the exhaust gas temperature rises.

  • TROUBLE JUDGMENT

  • Battery positive voltage is 8 – 16 V.
  • 2 seconds later after the ignition switch has been in “ON” position or the engine has started up.
  • Vehicle speed is 20 km/h or higher.
  • The No. 1 exhaust gas temperature sensor output voltage is 4.95 V or more.

  • PROBABLE CAUSES

  • Failed No. 1 exhaust gas temperature sensor
  • Open circuit or harness damage in No. 1 exhaust gas temperature sensor circuit or loose connector contact
  • Failed engine-ECU

  • DIAGNOSTIC PROCEDURE

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

  • Item 117: No. 1 exhaust gas temperature sensor
  • Q. Is the check result normal?

    STEP 2. Connector check: A-149 No. 1 exhaust gas temperature sensor connector

    Q. Is the check result normal?

    STEP 3. Check No. 1 exhaust gas temperature sensor itself.

    Q. Is the check result normal?

    STEP 4. Perform voltage measurement at A-149 No. 1 exhaust gas temperature sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 1 and earth.
  • Q. Is the check result normal?

    STEP 5. Connector check: C-105 engine-ECU connector.

    Q. Is the check result normal?

    STEP 6. Check harness between A-149 (terminal No. 1) No. 1 exhaust gas temperature sensor connector and C-105 (terminal No. 58) engine-ECU connector.

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

    STEP 7. M.U.T.-III data list

  • Item 117: No. 1 exhaust gas temperature sensor
  • Q. Is the check result normal?

    STEP 8. Perform resistance measurement at A-149 No. 1 exhaust gas temperature sensor connector.

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

    STEP 9. Connector check: C-105 engine-ECU connector

    Q. Is the check result normal?

    STEP 10. Check harness between A-149 (terminal No. 2) No. 1 exhaust gas temperature sensor connector and C-105 (terminal No. 82) engine-ECU connector.

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

    STEP 11. Connector check: C-105 engine-ECU connector.

    Q. Is the check result normal?

    STEP 12. Check harness between A-149 (terminal No. 1) No. 1 exhaust gas temperature sensor connector and C-105 (terminal No. 58) engine-ECU connector.

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

    Author: admin