SFI SYSTEM (w/ Secondary Air Injection System), Diagnostic DTC:P0031, P0032

DTC Code DTC Name
P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
P0032 Oxygen (A/F) Sensor Heater Control Circuit High (Bank 1 Sensor 1)

DESCRIPTION

Refer to DTC P2237 Click here.

Tech Tips


  • Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.

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

  • When one of these DTCs is stored, the ECM enters fail-safe mode. The ECM turns off the air fuel ratio 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 air fuel ratio sensor heater circuit uses a relay on the +B side of the circuit.

    A01J74QE36
DTC No. DTC Detection Condition Trouble Area
P0031 The heater current is less than the specified value while the heater is operating (1 trip detection logic).

  • Open in air fuel ratio sensor heater circuit

  • Air fuel ratio sensor heater (Sensor 1)

  • A/F relay

  • ECM
P0032 An Air Fuel Ratio (A/F) sensor heater current failure (1 trip detection logic).

  • Short in air fuel ratio sensor heater circuit

  • Air fuel ratio sensor heater (Sensor 1)

  • A/F relay

  • ECM

MONITOR DESCRIPTION

The ECM uses information from the air fuel ratio sensor to regulate the air-fuel ratio and keep it close to the stoichiometric level. This maximizes the ability of the Three-way Catalytic Converter (TWC) to purify the exhaust gases.

The air fuel ratio sensor detects oxygen levels in the exhaust gas and transmits the information to the ECM. The inner surface of the sensor element is exposed to the outside air. The outer surface of the sensor element is exposed to the exhaust gas. The sensor element is made of platinum coated zirconia and includes an integrated heating element.

The zirconia element generates a small voltage when there is a large difference in the oxygen concentrations between the exhaust gas and outside air. The platinum coating amplifies this voltage generation.

The air fuel ratio sensor is more efficient when heated. When the exhaust gas temperature is low, the sensor cannot generate useful voltage signals without supplementary heating. The ECM regulates the supplementary heating using a duty cycle approach to adjust the average current in the sensor heater element. If the heater current is outside the normal range, the signal transmitted by the air fuel ratio sensor becomes inaccurate. As a result, the ECM is unable to regulate the air-fuel ratio properly.

When the current in the air fuel ratio sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC.

MONITOR STRATEGY

Frequency of Operation Continuous

TYPICAL ENABLING CONDITIONS

P0031:
Heater output duty 30% or more
P0032:
Heater output duty More than 0%

CONFIRMATION DRIVING PATTERN

A01J681E21

  1. Connect the intelligent tester to the DLC3.

  2. Turn the ignition switch to ON and turn the intelligent tester on.

  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC operation).

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

  5. Turn the ignition switch to ON and turn the intelligent tester on [A].

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

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

  8. Idle the engine for 5 minutes or more [D].

  9. Enter the following menus: Powertrain / Engine and ECT / DTC [E].

  10. Read the pending DTCs.

    Tech Tips


    • If a pending DTC is output, the system is malfunctioning.

    • If a pending DTC is not output, perform the following procedure.

  11. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

  12. Input the DTC: P0031 or P0032.

  13. Check the DTC judgment result.

    Intelligent Tester Display Description
    NORMAL

    • DTC judgment completed

    • System normal
    ABNORMAL

    • DTC judgment completed

    • System abnormal
    INCOMPLETE

    • DTC judgment not completed

    • Perform driving pattern after confirming DTC enabling conditions
    N/A

    • Unable to perform DTC judgment

    • Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

    Tech Tips


    • If the judgment result shows NORMAL, the system is normal.

    • If the judgment result shows ABNORMAL, the system has a malfunction.

    • If the judgment result shows INCOMPLETE or N/A, perform steps [B] through [E] again.

WIRING DIAGRAM

Refer to DTC P2237 Click here.

INSPECTION PROCEDURE

Note

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

  • 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 AIR FUEL RATIO SENSOR (HEATER RESISTANCE)


    1. Inspect the air fuel ratio sensor Click here.


    NG

    REPLACE AIR FUEL RATIO SENSOR Click here

    OK

  2. CHECK TERMINAL VOLTAGE (+B OF AIR FUEL RATIO SENSOR)

    A01J4Y4E19
    Text in Illustration
    *a

    Front view of wire harness connector

    (to Air Fuel Ratio Sensor)

    1. Disconnect the air fuel ratio 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
      A49-2 (+B) - Body ground Ignition switch ON 11 to 14 V

    NG

    INSPECT A/F RELAY Click here

    OK

  3. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)


    1. Disconnect the air fuel ratio 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
      A49-1 (HA1A) - E11-1 (HT1A) Always Below 1 Ω
      A49-1 (HA1A) or E11-1 (HT1A) - 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. Start the engine.

    6. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

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

      Result
      Result Proceed to
      No pending DTC is output A
      Pending DTC P0031 or P0032 is output B

    B

    REPLACE ECM Click here

    A

    CHECK FOR INTERMITTENT PROBLEMS Click here

  5. INSPECT A/F RELAY


    1. Inspect the A/F relay Click here.


    NG

    REPLACE A/F RELAY

    OK

  6. CHECK HARNESS AND CONNECTOR (A/F RELAY - AIR FUEL RATIO SENSOR, NO. 1 INTEGRATION RELAY, BATTERY AND BODY GROUND)


    1. Remove the A/F relay from engine room relay block and junction block.

    2. Disconnect the cable from the positive (+) battery terminal.

    3. Disconnect the air fuel ratio sensor connector.

    4. Remove the No. 1 integration relay from the engine room relay block and junction block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A/F relay terminal 5 - Positive (+) battery cable terminal Always Below 1 Ω
      A/F relay terminal 1 - 1J-5 Always Below 1 Ω
      A49-2 (+B) - A/F relay terminal 3 Always Below 1 Ω
      A/F relay terminal 2 - Body ground Always Below 1 Ω
      A/F relay terminal 5 or Positive (+) battery cable terminal - Body ground Always 10 kΩ or higher
      A/F relay terminal 1 or 1J-5 - Body ground Always 10 kΩ or higher
      A49-2 (+B) or A/F relay terminal 3 - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    CHECK ECM POWER SOURCE CIRCUIT Click here