SFI SYSTEM (w/ Electronic Throttle Control System), Diagnostic DTC:P0135

DTC Code DTC Name
P0135 Oxygen (A/F) Sensor Heater Circuit (Bank 1 Sensor 1)

DESCRIPTION

In order to obtain a high purification rate for the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a Three-Way Catalytic Converter (TWC) is used. For the most efficient use of the TWC, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio. The heated oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This is used to detect the oxygen concentration in the exhaust gas and provide the ECM with feedback to control the air-fuel ratio. When the air-fuel ratio becomes lean, the oxygen concentration in the exhaust gas increases. The heated oxygen sensor informs the ECM of the lean condition (low voltage, i.e. less than 0.45 V). When the air-fuel ratio is richer than the stoichiometric air-fuel level, the oxygen concentration in the exhaust gas is reduced. And the heated oxygen sensor informs the ECM of the rich condition (high voltage, i.e. more than 0.45 V). The ECM judges by the voltage output of the heated oxygen sensor whether the air- fuel ratio is rich or lean and controls the injection time accordingly. If a malfunction of the heated oxygen sensor causes an output of abnormal voltage, the ECM is unable to perform accurate air-fuel ratio control. The heated oxygen sensor includes a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low), a current flows to the heater in order to heat the sensor for accurate oxygen concentration detection.

A0137QPE01

Tech Tips

The ECM provides a pulse width modulated control circuit to adjust current through the heater. The heated oxygen sensor heater circuit uses a relay on the +B side of the circuit.

A0138NYE01
DTC No. DTC Detection Condition Trouble Area
P0135 Open or short of heated oxygen sensor (sensor 1) heater or related circuit (3 trip detection logic).

  • Open or short in heated oxygen sensor (sensor 1) heater circuit

  • Heated oxygen sensor heater (sensor 1)

  • EFI relay

  • ECM

Tech Tips


  • DTC P0135 is detected when the engine idles for 1 minute.

  • Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.

  • Sensor 2 refers to the sensor mounted behind the TWC and located far from the engine assembly.

WIRING DIAGRAM

A0136ZHE01

INSPECTION PROCEDURE

Note

After replace the ECM, perform electronic throttle learning Click here.

Tech Tips

Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE


  1. INSPECT HEATED OXYGEN SENSOR (SENSOR RESISTANCE)


    1. A01370BE01

      Disconnect the B21 heated oxygen sensor connector (sensor 1).

    2. Measure the resistance between the terminals of the heated oxygen sensor connector.

      Standard resistance
      Tester Connection Specified Condition
      1 (HT) - 2 (+B) 6 to 14 Ω at 25°C (77°F)
      1 (HT) - 4 (E1) 10 kΩ or higher

    NG

    REPLACE HEATED OXYGEN SENSOR (SENSOR 1)

    OK

  2. CHECK TERMINAL VOLTAGE (+B OF HEATED OXYGEN SENSOR)


    1. A0137DVE06

      Disconnect the B21 heated oxygen sensor connector (sensor 1).

    2. Measure the voltage between the terminals of the B21 heated oxygen sensor connector and body ground.

      Standard voltage
      Tester Connection Specified Condition
      +B (B21-2) - Body ground 9 to 14 V

    3. Reconnect the heated oxygen sensor.


    OK

    CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM, HEATED OXYGEN SENSOR - EFI RELAY) Click here

    NG

  3. INSPECT ENGINE ROOM RELAY BLOCK (EFI RELAY)


    1. A0136ULE01

      Remove the engine room R/B.

    2. Remove the engine room R/B lower cover.

    3. Disconnect the 5 connectors from the engine room R/B.

    4. Measure the EFI relay resistance.

      Standard resistance
      Tester Connection Specified Condition
      1C-4 - 1C-5 10 kΩ or higher
      1C-4 - 1C-5

      Below 1 Ω

      (when battery voltage applied to terminals 1C-4 - 1C-8)

    5. Reinstall the engine room R/B.


    NG

    REPLACE ENGINE ROOM RELAY BLOCK

    OK

  4. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM, HEATED OXYGEN SENSOR - EFI RELAY)


    1. A0138KEE01

      Check the harness and the connectors between the ECM and the heated oxygen sensor.


      1. Disconnect the B21 heated oxygen sensor connector (sensor 1).

      2. Disconnect the B26 ECM connector.

      3. Measure the resistance.

        Standard resistance (check for open)
        Tester Connection Specified Condition
        HT (B21-1) - HT1A (B26-21) Below 1 Ω
        Standard resistance (check for short)
        Tester Connection Specified Condition
        HT (B21-1) or HT1A (B26-21) - Body ground 10 kΩ or higher

      4. Reconnect the ECM connector.

    2. Check the harness and the connectors between the heated oxygen sensor and EFI relay.


      1. Remove the engine room R/B.

      2. Remove the engine room R/B lower cover.

      3. Measure the resistance.

        Standard resistance (check for open)
        Tester Connection Specified Condition
        +B (B21-2) - Engine room R/B (1C-5) Below 1 Ω
        Standard resistance (check for short)
        Tester Connection Specified Condition
        +B (B21-2) or Engine room R/B (1C-5) - Body ground 10 kΩ or higher

      4. Reconnect the heated oxygen sensor connector.

      5. Reinstall the engine room R/B.


    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR

    OK

  5. CHECK IF DTC OUTPUT RECURS


    1. Start the engine.

    2. Allow the engine to idle for 1 minute or more.

    3. Connect the intelligent tester to the DLC3.

    4. Select the following menu items: Powertrain / Engine and ECT / DTC / Pending.

      Result
      Display (DTC Output) Proceed To
      No output A
      P0135 B

    B

    REPLACE ECM

    A

    GO TO "CHECK FOR INTERMITTENT PROBLEMS"