P0427 – No. 2 Exhaust Gas Temperature Sensor (catalyst temperature) Circuit Low Input Euro5b MMC L200 IV



OPERATION

  • A power voltage of 5 V is applied to the No. 2 exhaust gas temperature sensor (catalyst temperature) output terminal (terminal No. 1) from the engine-ECU (terminal No. 59).
  • The power voltage is earthed to the engine-ECU (terminal No. 83) from the No. 2 exhaust gas temperature sensor (catalyst temperature) (terminal No. 2).

  • FUNCTION

  • The No. 2 exhaust gas temperature sensor (catalyst temperature) converts the catalyst temperature into a voltage and inputs the voltage signal to the engine-ECU.
  • Engine-ECU uses this voltage output for DPF regeneration control.
  • The No. 2 exhaust gas temperature sensor (catalyst temperature) is a kind of resistor, which has characteristics to reduce its resistance as the catalyst temperature rises. Therefore, the sensor output voltage varies with the catalyst temperature, and becomes lower as the catalyst 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.
  • The No. 2 exhaust gas temperature sensor (catalyst temperature) output voltage is 0.255 V or less.

  • PROBABLE CAUSES

  • Failed No. 2 exhaust gas temperature sensor (catalyst temperature)
  • Short circuit in No. 2 exhaust gas temperature sensor (catalyst temperature) circuit or loose connector contact
  • Failed engine-ECU

  • DIAGNOSTIC PROCEDURE

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

  • Item 118: No. 2 exhaust gas temperature sensor (catalyst temperature)
  • Q. Is the check result normal?

    STEP 2. Connector check: A-159 No. 2 exhaust gas temperature sensor (catalyst temperature) connector

    Q. Is the check result normal?

    STEP 3. Check No. 2 exhaust gas temperature sensor (catalyst temperature) itself.

    Q. Is the check result normal?

    STEP 4. Connector check: C-105 engine-ECU connector

    Q. Is the check result normal?

    STEP 5. Check harness between A-159 (terminal No. 1) No. 2 exhaust gas temperature sensor (catalyst temperature) connector and C-105 (terminal No. 59) engine-ECU connector.

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

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

  • Item 118: No. 2 exhaust gas temperature sensor (catalyst temperature)
  • Q. Is the check result normal?

    Author: admin