Code No. P0137: Right Bank Oxygen Sensor (Rear) Circuit Low Voltage








OPERATION



  • The sensor signal is inputted to the engine-A/T-ECU (terminal No. 117) from the right bank oxygen sensor (rear) output terminal (terminal No. 4).
  • The right bank oxygen sensor (rear) (terminal No. 2) is earthed with engine-A/T-ECU (terminal No. 96).

FUNCTION



  • The right bank oxygen sensor (rear) 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 right bank 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-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 DTC P0136 and P0138 are not detected.
  • The engine coolant temperature is more than approximately 76°C.
  • Right bank oxygen sensor (front) output voltage is more than 0 V.
Judgment Criterion
  • Right bank oxygen sensor (rear) output voltage is less than 0.2 V.

PROBABLE CAUSES



  • Failed right bank oxygen sensor (rear)
  • Open/short circuit in right bank oxygen sensor (rear) 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 AD: Right bank 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-04 right bank 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-04 right bank oxygen sensor (rear) 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 C-04 (terminal No. 2) right bank oxygen sensor (rear) connector and D-217 (terminal No. 96) engine-A/T-ECU connector.
note Before checking harness, check intermediate connectors D-111 and D-225, 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 AD: Right bank 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-A/T-ECU.

STEP 7. Perform voltage measurement at C-04 right bank oxygen sensor (rear) connector.

  • Use special tool test harness (MB991316) 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 right bank oxygen sensor (rear) itself.



  • Check right bank oxygen sensor (rear) itself (Refer to ).

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

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

Q. Is the check result normal?

    Check intermediate connector D-225, and repair if necessary. If intermediate connector is normal, check and repair harness between C-04 (terminal No. 4) right bank oxygen sensor (rear) connector and D-217 (terminal No. 117) 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.