Code No. P0135: Oxygen Sensor (front) Heater System <M/T>










OPERATION



  • Power is supplied to the heater power terminal (terminal No. 1) of the oxygen sensor (front) connector from the engine control relay (terminal No. 2).
  • The heater (terminal No. 2) of the oxygen sensor (front) connector is controlled by the power transistor in the engine-ECU (terminal No. 34).

FUNCTION



  • The power supply to the oxygen sensor (front) heater is controlled by the ON/OFF control of the power transistor in the engine-ECU.
  • Heating the oxygen sensor (front) heater enables the oxygen sensor (front) to provide good response even when the exhaust emission temperature is low.

TROUBLE JUDGMENT


Check Conditions
  • Excluding when the ignition switch is in ON position or during cranking
  • Engine coolant temperature is more than 20°C.
  • The engine coolant temperature sensor is normal.
  • While oxygen sensor (front) heater is ON.
  • Battery positive voltage is more than 11 V and is less than 16 V.
Judgment Criterion
  • Oxygen sensor heater (front) currents has continued to be less than 0.16 A.


  • Oxygen sensor heater (front) currents has continued to be more than 7.5 A.

FAIL-SAFE AND BACKUP FUNCTION



  • None

PROBABLE CAUSES



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

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-45 oxygen sensor (front) connector

Q. Is the check result normal?
Go to Step 2 .
Repair or replace the connector.

STEP 2. Perform resistance measurement at C-45 oxygen sensor (front) connector.

  • Disconnect connector, and measure at sensor side.
  • Resistance between terminal No. 1 and No. 2.
OK: 5 - 30 Ω (at 20°C)

Q. Is the check result normal?
Go to Step 3 .
Replace the oxygen sensor (front).

STEP 3. Perform voltage measurement at C-45 oxygen sensor (front) connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 1 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 5 .
Go to Step 4 .

STEP 4. Connector check: A-33X engine control relay connector

Q. Is the check result normal?

    Check and repair harness between C-45 (terminal No. 1) oxygen sensor (front) connector and A-33X (terminal No. 2) engine control relay connector.

    • Check power supply line for open/short circuit.
Repair or replace the connector.

STEP 5. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?
Go to Step 6 .
Repair or replace the connector.

STEP 6. Perform voltage measurement at B-08 engine-ECU connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 34 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 7 .

    Check intermediate connector A-11, and repair if necessary. If intermediate connector is normal check and repair harness between C-45 (terminal No. 2) oxygen sensor (front) connector and B-08 (terminal No. 34) engine-ECU connector.

    • Check earthing line for open/short circuit.

STEP 7. Check harness between C-45 (terminal No. 1) oxygen sensor (front) connector and A-33X (terminal No. 2) engine control relay connector.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 8 .
Repair the damaged harness wire.

STEP 8. Check harness between C-45 (terminal No. 2) oxygen sensor (front) connector and B-08 (terminal No. 34) engine-ECU connector.
note Before checking harness, check intermediate connector A-11, and repair if necessary.

  • Check earthing line for damage.

Q. Is the check result normal?
Go to Step 9 .
Repair the damaged harness wire.

STEP 9. M.U.T.-III diagnosis code

  • Reconfirmation of diagnosis code.

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