Code No. P0136: Oxygen Sensor (rear) System <A/T>








OPERATION



  • The oxygen sensor (rear) (terminal No. 3) outputs a sensor signal, which is input into the engine-ECU (terminal No. 40).
  • The power voltage is earthed to the engine-ECU (terminal No. 41) from the oxygen sensor (rear) (terminal No. 4).

FUNCTION



  • The oxygen sensor (rear) converts the concentration of oxygen in the exhaust emission into a voltage and inputs the signal to the engine-ECU.
  • When the air-fuel ratio is richer than the theoretical air-fuel ratio, the oxygen sensor (rear) 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-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
  • Above 4 minutes later after the engine has started up.
  • The engine coolant temperature is more than 82°C for 5 seconds or longer.
  • The engine coolant temperature sensor is normal.
  • The engine speed is more than 1,200 r/min for 5 seconds or longer.
  • Manifold absolute pressure is more than 20 kPa for 5 seconds or longer.
Judgment Criterion
  • When a power voltage of 5 V is applied to the oxygen sensor (rear), the sensor output voltage is 4.0 V or more.

FAIL-SAFE AND BACKUP FUNCTION



  • None

PROBABLE CAUSES



  • Failed oxygen sensor (rear)
  • Open/short circuit or harness damage in oxygen sensor (rear) circuit or loose connector contact
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

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

  • Refer to Data List Reference Table .

  1. Item AD: Oxygen sensor (rear)

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: C-22 oxygen sensor (rear) connector

Q. Is the check result normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. Perform resistance measurement at C-22 oxygen sensor (rear) connector.

  • Disconnect connector, and measure at harness side.
  • Resistance between terminal No. 4 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: B-08 engine-ECU connector

Q. Is the check result normal?
Go to Step 5 .
Repair or replace the connector.

STEP 5. Check harness between C-22 (terminal No. 4) oxygen sensor (rear) connector and B-08 (terminal No. 41) engine-ECU connector.
note Before checking harness, check intermediate connector A-11, and repair if necessary.

  • Check earthing line for open circuit and 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 AD: Oxygen sensor (rear)

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 7. Perform voltage measurement at C-22 oxygen sensor (rear) connector.

  • Use special tool test harness (MB991658) to connect connector, and measure at pick-up harness.
  • Accelerate the engine at full throttle in the 2nd gear to keep the engine speed at 3,500 r/min or more.
  • Voltage between terminal No. 3 and earth.
OK: 0.6 - 1.0 V

Q. Is the check result normal?
Go to Step 10 .
Go to Step 8 .

STEP 8. Check oxygen sensor (rear) itself.

  • Check oxygen sensor (rear) (Refer to ).

Q. Is the check result normal?
Go to Step 9 .
Replace the oxygen sensor (rear).

STEP 9. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?

    Check intermediate connector A-11, and repair if necessary.If intermediate connector is normal, check and repair harness between C-22 (terminal No. 3) oxygen sensor (rear) connector and B-08 (terminal No. 40) engine-ECU connector.

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

STEP 10. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?
Go to Step 11 .
Repair or replace the connector.

STEP 11. Perform voltage measurement at B-08 engine-ECU connector.

  • Disconnect engine-ECU harness, and connect special tool power plant ECU check harness (MB992110) to measure at connector for inspection.
  • Accelerate the engine at full throttle in the 2nd gear to keep the engine speed at 3,500 r/min or more.
  • Voltage between terminal No. 40 and earth.
OK: 0.6 - 1.0 V

Q. Is the check result normal?
Go to Step 6 .
Go to Step 12 .

STEP 12. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?

    Check intermediate connector A-11, and repair if necessary.If intermediate connector is normal, check and repair harness between C-22 (terminal No. 3) oxygen sensor (rear) connector and B-08 (terminal No. 40) engine-ECU connector.

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