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 diagnosis code No. P0136 and No. 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.