SFI SYSTEM, Diagnostic DTC:P0037, P0038, P0057, P0058

DTC Code DTC Name
P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
P0038 Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2)
P0057 Oxygen Sensor Heater Control Circuit Low (Bank 2 Sensor 2)
P0058 Oxygen Sensor Heater Control Circuit High (Bank 2 Sensor 2)

DESCRIPTION

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a TWC (Three-Way Catalytic Converter) 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 level. For the purpose of helping the ECM to deliver accurate air-fuel ratio control, a Heated Oxygen (HO2) sensor is used.

The HO2 sensor is located behind the TWC, and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen concentration even when the intake air volume is low (the exhaust gas temperature is low).

When the air-fuel ratio becomes lean, the oxygen concentration in the exhaust gas is rich. The HO2 sensor informs the ECM that the post-TWC air-fuel ratio is lean (low voltage, i.e. less than 0.45 V).

Conversely, when the air-fuel ratio is richer than the stoichiometric air-fuel level, the oxygen concentration in the exhaust gas becomes lean. The HO2 sensor informs the ECM that the post-TWC air-fuel ratio is rich (high voltage, i.e. more than 0.45 V). The HO2 sensor has the property of changing its output voltage drastically when the air-fuel ratio is close to the stoichiometric level.

The ECM uses the supplementary information from the HO2 sensor to determine whether the air-fuel ratio after the TWC is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the HO2 sensor is working improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air-fuel ratio control.

A01GNGKE09

Tech Tips


  • Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.

  • When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the Heated Oxygen (HO2) Sensor heater in fail-safe mode. Fail-safe mode continues until the engine switch is turned off.

  • The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The HO2 sensor heater circuit uses a relay on the +B side of the circuit.

    A01GL2SE04
DTC No. DTC Detection Condition Trouble Area

P0037

P0057

 Heated Oxygen (HO2) sensor heater current less than 0.3 A (1 trip detection logic)

  • Open in heated oxygen (HO2) sensor heater circuit

  • HO2 sensor heater

  • ECM

P0038

P0058

 Heated Oxygen (HO2) sensor heater current more than 2 A (1 trip detection logic)

  • Short in HO2 sensor heater circuit

  • HO2 sensor heater

  • ECM

Tech Tips


  • Bank 1 refers to the bank that includes No. 1 cylinder.

  • Bank 2 refers to the bank that does not include No. 1 cylinder.

  • Sensor 1 refers to the sensor closest to the engine assembly.

  • Sensor 2 refers to the sensor farthest away from the engine assembly.

MONITOR DESCRIPTION

The sensing portion of the Heated Oxygen (HO2) sensor has a zirconia element which is used to detect the oxygen concentration in the exhaust gas. If the zirconia element is at the appropriate temperature, and the difference between the oxygen concentrations surrounding the inside and outside surfaces of the sensor is large, the zirconia element generates voltage signals. In order to increase the oxygen concentration detecting capacity of the zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element inside the sensor.

Heated oxygen sensor heater range check (P0037, P0038, P0057 and P0058):

WIRING DIAGRAM

Refer to DTC P0136 Click here.

INSPECTION PROCEDURE

Tech Tips

Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. 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 (HEATER RESISTANCE)


    1. A01GI73E04

      Disconnect the L50, L49 or E58 HO2 sensor connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance (Bank 1 Sensor 2)
      Tester Connection Condition Specified Condition
      1 (HT1B) - 2 (+B) 20°C (68°F) 11 to 16 Ω
      1 (HT1B) - 4 (E2) Always 10 kΩ or higher
      Standard resistance (Bank 2 Sensor 2)
      Tester Connection Condition Specified Condition
      1 (HT2B) - 2 (+B) 20°C (68°F) 11 to 16 Ω
      1 (HT2B) - 4 (E2) Always 10 kΩ or higher
      Result
      Result Proceed to
      OK A
      NG (for 2WD) B
      NG (for AWD) C

    B

    REPLACE HEATED OXYGEN SENSOR Click here

    C

    REPLACE HEATED OXYGEN SENSOR Click here

    A

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


    1. A01GNCME03

      Disconnect the L50, L49 or E58 HO2 sensor connector.

    2. Turn the engine switch on (IG).

    3. Measure the voltage according to the value(s) in the table below.

      Standard voltage (Bank 1 Sensor 2)
      Tester Connection Switch Condition Specified Condition
      L50-2 (+B) - Body ground Engine switch on (IG) 11 to 14 V
      E58-2 (+B) - Body ground Engine switch on (IG) 11 to 14 V
      Standard voltage (Bank 2 Sensor 2)
      Tester Connection Switch Condition Specified Condition
      L49-2 (+B) - Body ground Engine switch on (IG) 11 to 14 V

    NG

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

    OK

  3. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)


    1. A01GNNQE02

      Check the harness and connector between the ECM and HO2 sensor.


      1. Disconnect the L50, L49 or E58 HO2 sensor connector.

      2. Disconnect the A13 ECM connector.

      3. Measure the resistance according to the value(s) in the table below.

        Standard resistance (Check for open)
        Terminal Connection Condition Specified Condition
        L50-1 (HT1B) - A13-4 (HT1B) Always Below 1 Ω
        E58-1 (HT1B) - A13-4 (HT1B) Always Below 1 Ω
        L49-1 (HT2B) - A13-3 (HT2B) Always Below 1 Ω
        Standard resistance (Check for short)
        Terminal Connection Condition Specified Condition
        L50-1 (HT1B) or A13-4 (HT1B) - Body ground Always 10 kΩ or higher
        E58-1 (HT1B) or A13-4 (HT1B) - Body ground Always 10 kΩ or higher
        L49-1 (HT2B) or A13-3 (HT2B) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE ECM Click here

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


    1. A01GJS2E02

      Check the harness and connector between the HO2 sensor and EFI relay (EFI MAIN2).


      1. Remove the EFI MAIN2 relay from the engine room No. 2 relay block.

      2. Disconnect the L50, L49 or E58 HO2 sensor connector.

      3. Measure the resistance according to the value(s) in the table below.

        Standard resistance (Check for open)
        Terminal Connection Condition Specified Condition
        EFI MAIN2 relay (3) - L50-2 (+B) Always Below 1 Ω
        EFI MAIN2 relay (3) - E58-2 (+B) Always Below 1 Ω
        EFI MAIN2 relay (3) - L49-2 (+B) Always Below 1 Ω
        Standard resistance (Check for short)
        Terminal Connection Condition Specified Condition
        EFI MAIN2 relay (3) or L50-2 (+B) - Body ground Always 10 kΩ or higher
        EFI MAIN2 relay (3) or E58-2 (+B) - Body ground Always 10 kΩ or higher
        EFI MAIN2 relay (3) or L49-2 (+B) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    CHECK ECM POWER SOURCE CIRCUIT Click here