SFI SYSTEM (w/ Secondary Air Injection System), Diagnostic DTC:P0037, P0038, P0141

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)
P0141 Oxygen Sensor Heater Circuit (Bank 1 Sensor 2)

DESCRIPTION


Tech Tips


  • When any of these DTCs is stored, the ECM enters fail-safe mode. The ECM turns off the heated oxygen sensor heater in fail-safe mode. The ECM continues operating in fail-safe mode until the ignition 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.

    A003ERVE34
DTC No. DTC Detection Condition Trouble Area
P0037

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 (Sensor 2)

  • No. 1 integration relay

  • ECM
P0038

Heated oxygen sensor heater current 2 A or more.

(1 trip detection logic)

  • Short in heated oxygen sensor heater circuit

  • Heated oxygen sensor heater (Sensor 2)

  • No. 1 integration relay

  • ECM
P0141

The cumulative heater resistance correction value exceeds the threshold.

(2 trip detection logic)

  • Open or short in heated oxygen sensor heater circuit

  • Heated oxygen sensor heater (Sensor 2)

  • No. 1 integration relay

  • ECM

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 and P0038):

The ECM monitors the current applied to the heated oxygen sensor heater to check the heater for malfunctions.

If the current is below the threshold value, the ECM determines that there is an open circuit in the heater.

If the current is above the threshold value, the ECM determines that there is a short circuit in the heater.

The ECM constantly monitors the current applied to the heater. If the ECM detects an open or short circuit, the ECM turns the MIL on and sets a DTC.

If a malfunction is detected, the ECM cuts off the current applied to the heater.

Example:

The ECM sets DTC P0038 when the current in the heated oxygen sensor heater is more than 2 A. Conversely, when the heater current is less than 0.3 A, DTC P0037 is set.

Heated oxygen sensor heater performance (P0141):

After the accumulated heater ON time exceeds 100 seconds, the ECM calculates the heater resistance using battery voltage and the current applied to the heater. If the resistance is above the threshold value, the ECM determines that there is a malfunction in the heated oxygen sensor heater and stores DTC P0141.

WIRING DIAGRAM

A003CMQE01

INSPECTION PROCEDURE

Note

Inspect the fuses of circuits related to this system before performing the following inspection procedure.

Tech Tips


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

  • 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.

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

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

PROCEDURE


  1. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)


    1. Inspect the heated oxygen sensor Click here.


    NG

    REPLACE HEATED OXYGEN SENSOR Click here

    OK

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

    A003EUVE52
    Text in Illustration
    *a

    Front view of wire harness connector

    (to Heated Oxygen Sensor)

    1. Disconnect the heated oxygen sensor connector.

    2. Turn the ignition switch to ON.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      D35-2 (+B) - Body ground Ignition switch ON 11 to 14 V

    NG

    INSPECT NO. 1 INTEGRATION RELAY (EFI) Click here

    OK

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


    1. 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
      Tester Connection Condition Specified Condition
      D35-1 (HT1B) - D97-63 (HT1B) Always Below 1 Ω
      D35-1 (HT1B) or D97-63 (HT1B) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK WHETHER DTC OUTPUT RECURS


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the intelligent tester on.

    4. Clear the DTCs Click here.

    5. Turn the ignition switch off and wait for at least 30 seconds.

    6. Start the engine and idle it for 5 minutes or more.

    7. With the vehicle stationary, depress the accelerator pedal and maintain an engine speed of 3000 rpm for 1 minute.

    8. Idle the engine for 5 minutes or more.

    9. Read the output pending DTCs using the intelligent tester.

      Result
      Result Proceed to
      No pending DTC is output A
      Pending DTC P0037, P0038 and/or P0141 is output B

    B

    REPLACE ECM Click here

    A

    CHECK FOR INTERMITTENT PROBLEMS Click here

  5. INSPECT NO. 1 INTEGRATION RELAY (EFI)


    1. Inspect the No. 1 integration relay (EFI) Click here.


    NG

    REPLACE NO. 1 INTEGRATION RELAY

    OK

  6. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - NO. 1 INTEGRATION RELAY)


    1. Disconnect the heated oxygen sensor connector.

    2. Remove the No. 1 integration relay from the No. 1 engine room relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      D35-2 (+B) - 10A-8 Always Below 1 Ω
      D35-2 (+B) or 10A-8 - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    CHECK ECM POWER SOURCE CIRCUIT Click here