Code No. P0151: Left Bank Oxygen Sensor (Front) Circuit Low Voltage










OPERATION



  • The sensor signal is inputted to the engine-A/T-ECU (terminal No. 108) from the left bank oxygen sensor (front) output terminal (terminal No. 4).
  • The left bank oxygen sensor (front) (terminal No. 2) is earthed with engine-A/T-ECU (terminal No. 96).

FUNCTION



  • The left bank oxygen sensor (front) converts the concentration of oxygen in the exhaust emission into a voltage and inputs the signal to the engine-A/T-ECU.
  • When the air-fuel ratio is richer than the theoretical air-fuel ratio, the left bank oxygen sensor (front) outputs a voltage of about 1 V. When it is leaner than the theoretical air-fuel ratio, it outputs a voltage of about 0 V.
  • In response to the signal, the engine-A/T-ECU controls the fuel injection amount so that the air-fuel ratio can be equivalent to the theoretical air-fuel ratio.

TROUBLE JUDGMENT


Check Conditions
  • Malfunctions regarding diagnosis code No. P0150 and No. P0152 are not detected.
  • The engine coolant temperature is more than approximately 76°C.
Judgment Criterion
  • Left bank oxygen sensor (front) output voltage is less than 0.2 V.

PROBABLE CAUSES



  • Failed left bank oxygen sensor (front)
  • Open/short circuit in left bank oxygen sensor (front) circuit or loose connector contact
  • Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE


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



  • Refer to Data List Reference Table .

  1. Item AE: Left bank 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. Connector check: B-23 left bank oxygen sensor (front) connector


Q. Is the check result normal?

Go to Step 3.
Repair or replace the connector.

STEP 3. Perform resistance measurement at B-23 left bank oxygen sensor (front) connector.



  • Disconnect connector, and measure at harness side.
  • Resistance between terminal No. 2 and earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?

Go to Step 7.
Go to Step 4.

STEP 4. Connector check: D-217 engine-A/T-ECU connector


Q. Is the check result normal?

Go to Step 5.
Repair or replace the connector.

STEP 5. Check harness between B-23 (terminal No. 2) left bank oxygen sensor (front) connector and D-217 (terminal No. 96) engine-A/T-ECU connector.


note Before checking harness, check intermediate connector D-111, and repair if necessary.

  • Check earthing line for damage.

Q. Is the check result normal?

Go to Step 6.
Repair the damaged harness wire.

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



  • Refer to Data List Reference Table .

  1. Item AE: Left bank 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-A/T-ECU.

STEP 7. Perform voltage measurement at B-23 left bank oxygen sensor (front) connector.



  • Use special tool test harness (MD998464) to connect connector, and measure at pick-up harness.
  • Engine: After warm-up
  • Transmission: P range
  • Voltage between terminal No. 4 and earth.
OK:
    When the engine is 2,500 r/min, the output voltage should repeat 0 to 0.8 V alternately.

Q. Is the check result normal?

Go to Step 10.
Go to Step 8.

STEP 8. Check left bank oxygen sensor (front) itself.



  • Check left bank oxygen sensor (front) itself (Refer to ).

Q. Is the check result normal?

Go to Step 9.
Replace the left bank oxygen sensor (front).

STEP 9. Connector check: D-217 engine-A/T-ECU connector


Q. Is the check result normal?


    Check and repair harness between B-23 (terminal No. 4) left bank oxygen sensor (front) connector and D-217 (terminal No. 108) engine-A/T-ECU connector.

    • Check output line for short circuit and damage.
Repair or replace the connector.

STEP 10. Connector check: D-217 engine-A/T-ECU connector


Q. Is the check result normal?


    Go to Step 6.
Repair or replace the connector.