P0141 – Oxygen sensor (Rear) Heater System MMC Colt



OPERATION

  • Power is supplied to the heater power terminal (terminal No. 4) of the oxygen sensor (rear) connector from the engine control relay (terminal No. 4).
  • The heater (terminal No. 3) of the oxygen sensor (rear) is controlled by the power transistor in the engine-ECU (terminal No. 94).

  • FUNCTION

  • The power supply to the oxygen sensor (rear) heater is controlled by the ON/OFF control of the power transistor in the engine-ECU.
  • Heating the oxygen sensor (rear) heater enables the oxygen sensor (rear) to provide good response even when the exhaust emission temperature is low.

  • TROUBLE JUDGMENT

  • 60 seconds have elapsed since the previous monitoring started.
  • Engine coolant temperature is 20°C or higher.
  • While oxygen sensor (rear) heater is on.
  • Battery positive voltage is 11 – 16 V.
  • Oxygen sensor (rear) heater currents have continued to be 0.16 A or lower, or 5.0 A or higher for 4 seconds.

  • PROBABLE CAUSES

  • Failed oxygen sensor (rear) heater
  • Open or shorted oxygen sensor (rear) heater circuit, harness damage, or connector damage
  • Failed engine-ECU

  • DIAGNOSIS PROCEDURE

    STEP 1. Connector check: C-24 oxygen sensor (rear) connector

    Q. Is the check result normal?

    STEP 2. Perform resistance measurement at C-24 oxygen sensor (rear) connector.

  • Disconnect connector, and measure at sensor side.
  • Resistance between terminal No. 3 and No. 4.
  • Q. Is the check result normal?

    STEP 3. Perform voltage measurement at C-24 oxygen sensor (rear) connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 4 and earth.
  • Q. Is the check result normal?

    STEP 4. Connector check: B-206 engine control relay connector

    Q. Is the check result normal?

  • Check power supply line for open/short circuit.
  • STEP 5. 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.
  • Ignition switch: ON
  • Voltage between terminal No. 94 and earth.
  • Q. Is the check result normal?

    STEP 6. Connector check: A-09 engine-ECU connector

    Q. Is the check result normal?

    STEP 7. Check harness between C-24 (terminal No. 3) oxygen sensor (rear) connector and A-09 (terminal No. 94) engine-ECU connector.

  • Check earthing line for open/short circuit.
  • 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 C-24 (terminal No. 4) oxygen sensor (rear) connector and B-206 (terminal No. 4) engine control relay connector.

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

    STEP 10. Check harness between C-24 (terminal No. 3) oxygen sensor (rear) connector and A-09 (terminal No. 94) engine-ECU connector.

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

    STEP 11. M.U.T.-III diagnosis code.

  • Reconfirmation of diagnosis code.
  • Q. Is the diagnosis code set?

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