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 three way catalytic converter is used. For the most efficient use of the three way catalytic converter, 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 sensor is used.

The heated oxygen sensor is located behind the three way catalytic converter, 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 heated oxygen sensor informs the ECM that the post three way catalytic converter 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 heated oxygen sensor informs the ECM that the post three way catalytic converter air fuel ratio is rich (high voltage, i.e. more than 0.45 V). The heated oxygen 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 heated oxygen sensor to determine whether the air fuel ratio after the three way catalytic converter is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the heated oxygen sensor is working improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air fuel ratio control.

A0160KCE01

Tech Tips


  • Sensor 2 refers to the sensor mounted behind the three way catalytic converter 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 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 heated oxygen sensor heater circuit uses a relay on the +B side of the circuit.

    A015Z0UE04
DTC No. DTC Detection Condition Trouble Area

P0037

P0057

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

  • Open in heated oxygen sensor heater circuit

  • Heated oxygen sensor heater

  • ECM

P0038

P0058

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

  • Short in heated oxygen sensor heater circuit

  • Heated oxygen 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 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 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. A016135E81

      Disconnect the heated oxygen 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

    3. Reconnect the heated oxygen sensor connector.


    NG

    REPLACE HEATED OXYGEN SENSOR Click here

    OK

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


    1. A015ZEBE18

      Disconnect the heated oxygen 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
      J68-2 (+B) - Body ground Engine switch on (IG) 11 to 14 V
      Standard Voltage (Bank 2 Sensor 2)
      Tester Connection Switch Condition Specified Condition
      J40-2 (+B) - Body ground Engine switch on (IG) 11 to 14 V

    4. Reconnect the heated oxygen sensor connector.


    NG

    INSPECT FUSE (EFI NO. 2 FUSE) Click here

    OK

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


    1. A0162D2E09

      Disconnect the heated oxygen sensor connector.

    2. Disconnect the 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
      J68-1 (HT1B) - A6-4 (HT1B) Always Below 1 Ω
      J40-1 (HT2B) - A6-3 (HT2B) Always Below 1 Ω
      Standard Resistance (Check for Short)
      Terminal Connection Condition Specified Condition
      J68-1 (HT1B) or A6-4 (HT1B) - Body ground Always 10 kΩ or higher
      J40-1 (HT2B) or A6-3 (HT2B) - Body ground Always 10 kΩ or higher

    4. Reconnect the heated oxygen sensor connector.

    5. Reconnect the ECM connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (HEATED OXYGEN SENSOR - ECM)

    OK

    REPLACE ECM Click here

  4. INSPECT FUSE (EFI NO. 2 FUSE)


    1. A015YXDE06

      Remove the EFI No. 2 fuse from the engine room No. 2 relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      EFI No. 2 fuse Always Below 1 Ω

    3. Reinstall the EFI No. 2 fuse.


    NG

    REPLACE FUSE (EFI NO. 2 FUSE)

    OK

    REPAIR OR REPLACE HARNESS OR CONNECTOR (EFI MAIN RELAY - HEATED OXYGEN SENSOR)