Code No. P0131: Oxygen Sensor (front) Circuit Low Voltage




OPERATION




FUNCTION




TROUBLE JUDGEMENT


Check Conditions
Judgement Criterion

FAIL-SAFE AND BACKUP FUNCTION




PROBABLE CAUSES




DIAGNOSIS PROCEDURE


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



  • Data list reference table (Refer to ).

    1. Item AC: Oxygen sensor (front)

Q. Is the check result normal?

Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Go to Step 2.

STEP 2. Perform voltage measurement at oxygen sensor (front) connector.



  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal engine-ECU OFLE line and body earth.
OK: 0.4 - 0.6 V

Q. Is the check result normal?

Go to Step 5.
Go to Step 3.

STEP 3. Check of open circuit, and short circuit in OFLE line between oxygen sensor (front) connector and engine-ECU connector.


Q. Is the check result normal?

Go to Step 4.
Repair the connector(s) or wiring harness.

STEP 4. M.U.T.-III data list



  • Data list reference table (Refer to ).

    1. Item AC: Oxygen sensor (front)

Q. Is the check result normal?

Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Replace the engine-ECU.

STEP 5. Check of damage in OFLE line between oxygen sensor (front) connector and engine-ECU connector.


Q. Is the check result normal?

Go to Step 6.
Repair the connector(s) or wiring harness.

STEP 6. Perform voltage measurement at oxygen sensor (front) connector.



  • Use special tool test harness (MB991658) to connect connector, and measure at pick-up harness.
  • Engine: After warm-up
  • Transmission: Neutral
  • Voltage between terminal engine-ECU O2FL line and earth.
OK:
    When the engine is 2,500 r/min, the output voltage should repeat 0.9 V or less <=> 1.1 to 1.5 V alternately.

Q. Is the check result normal?

Go to Step 8.
Go to Step 7.

STEP 7. Check oxygen sensor (front) itself.



  • Oxygen sensor check (Refer to ).

Q. Is the check result normal?


    Repair or replace the connector(s), or check and repair the harness of short circuit in O2FL line between oxygen sensor (front) connector and engine-ECU connector.
Replace oxygen sensor (front).

STEP 8. Check of open circuit, and damage in O2FL line between oxygen sensor (front) connector and engine-ECU connector.


Q. Is the check result normal?

Go to Step 4.
Repair the connector(s) or wiring harness.





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