Posted in Mitsubishi Colt

P0125 – Feedback System Monitor MMC Colt

 Posted by  Posted on September 26, 2020

FUNCTION

  • The engine-ECU effects air-fuel ratio feedback control in accordance with the signals from the oxygen sensor (front).
  • If the oxygen sensor (front) has deteriorated, corrections will be made by the oxygen sensor (rear).
  • Diagnosis code P0125 becomes stored in memory if a failure is detected in the above air/fuel ratio feedback control system.

    • TROUBLE JUDGMENT

  • The engine coolant temperature approximately. 76°C or more.
  • Within the range of air-fuel ratio feedback operation.
  • Not in low speed operation.
  • The oxygen sensor output voltage is not deviated from 0.5 V for 30 seconds.

    • PROBABLE CAUSES

  • Failed oxygen sensor (front)
  • Harness damage in oxygen sensor (front) circuit, or connector damage
  • Failed oxygen sensor (rear)
  • Failed fuel system
  • Failed exhaust system
  • Air drawn in from gaps in gasket, seals, etc.
  • Failed engine-ECU

    • DIAGNOSIS PROCEDURE

    STEP 1. M.U.T.-III diagnosis code

    Q. Is any other diagnosis code than P0125 output?

    STEP 2. M.U.T.-III data list

  • Item No. 7: Manifold absolute pressure sensor
  • Item No. 8: Engine coolant temperature sensor
  • Item No. 9: Oxygen sensor (rear)

    • Q. Are the check results normal?

    STEP 3. Check for intake of air from gaps in gasket, seals, etc.

    Q. Is the check result normal?

    STEP 4. Check for leakage of exhaust emission from exhaust manifold.

    Q. Is the check result normal?

    STEP 5. Check throttle body (throttle valve portion) for contamination.

    Q. Is the check result normal?

    STEP 6. Connector check: B-108 oxygen sensor (front) connector, A-09 engine-ECU connector.

    Q. Is the check result normal?

    STEP 7. Check B-108 oxygen sensor (front) itself.

    Q. Is the check result normal?

    STEP 8. Check harness between B-108 (terminal No. 1) oxygen sensor (front) connector and A-09 (terminal No. 97) engine-ECU connector.

  • Check output line for damage.

    • Q. Is the check result normal?

    STEP 9. Connector check: Injector connector

  • A-101 (No. 1 injector connector)
  • A-102 (No. 2 injector connector)
  • A-123 (No. 3 injector connector)

    • Q. Is the check result normal?

    STEP 10. Check injector itself.

    Q. Is the check result normal?

    STEP 11. Connector check: B-206 engine control relay connector and A-08 engine-ECU connector.

    Q. Is the check result normal?

    STEP 12. Check harness between B-206 engine control relay connector and injector connector.

  • Check harness between B-206 (terminal No. 4) engine control relay connector and A-101 (terminal No. 1) No. 1 injector connector.
  • Check harness between B-206 (terminal No. 4) engine control relay connector and A-102 (terminal No. 1) No. 2 injector connector.
  • Check harness between B-206 (terminal No. 4) engine control relay connector and A-123 (terminal No. 1) No. 3 injector connector.
    note Before checking harness, check intermediate connectors B-212 and A-13, and repair if necessary.
  • Check power supply line for damage.

    • Q. Are the check results normal?

    STEP 13. Check harness between injector connector and A-08 engine-ECU connector.

  • Check harness between A-101 (terminal No. 2) No. 1 injector connector and A-08 (terminal No. 8) engine-ECU connector.
  • Check harness between A-102 (terminal No. 2) No. 2 injector connector and A-08 (terminal No. 9) engine-ECU connector.
  • Check harness between A-123 (terminal No. 2) No. 3 injector connector and A-08 (terminal No. 23) engine-ECU connector.
  • Check earthing line for damage.

    • Q. Are the check results normal?

    STEP 14. Fuel pressure measurement.

    Q. Is the check result normal?

    P0125 MMC pajero

    Author: admin