SFI SYSTEM, Diagnostic DTC:P0031, P0032, P101D

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)
P101D A/F Sensor Heater Circuit Performance Bank 1 Sensor 1 Stuck ON

DESCRIPTION

Refer to DTC P2195 Click here.

Tech Tips


  • When any 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.

  • 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.

  • 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.

    A01DR3QE01
DTC No. DTC Detection Condition Trouble Area
P0031 The heater current is below 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

  • ECM power source circuit

  • ECM
P0032 An air fuel ratio sensor heater current failure (1 trip detection logic).

  • Short in air fuel ratio sensor heater circuit

  • Air fuel ratio sensor heater

  • ECM power source circuit

  • ECM
P101D The heater current is higher than the specified value while the heater is not operating (1 trip detection logic). ECM

Tech Tips


  • 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 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.

WIRING DIAGRAM

Refer to DTC P2195 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.

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 (POWER SOURCE)

    A01DQPAE02
    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
      C56-2 (+B) - Body ground Ignition switch ON 11 to 14 V

    4. Reconnect the air fuel ratio sensor connector.


    NG

    INSPECT INTEGRATION RELAY (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 (Check for Open)
      Tester Connection Condition Specified Condition
      C56-1 (HA1A) - C63-6 (HA1A) Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      C56-1 (HA1A) or C63-6 (HA1A) - Body ground Always 10 kΩ or higher

    4. Reconnect the air fuel ratio sensor connector.

    5. Reconnect the ECM connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  4. CHECK WHETHER DTC OUTPUT RECURS (DTC P0031, P0032 OR P101D)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the intelligent tester on.

    4. Clear DTCs Click here.

    5. Start the engine.

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

    7. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

    8. Read DTCs.

      Result
      Result Proceed to
      DTC is not output A
      DTC P0031, P0032 or P101D is output B

    B

    REPLACE ECM Click here

    A

    CHECK FOR INTERMITTENT PROBLEMS Click here

  5. INSPECT INTEGRATION RELAY (A/F RELAY)


    1. Inspect the integration relay (A/F relay) Click here.


    NG

    REPLACE INTEGRATION RELAY

    OK

  6. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - INTEGRATION RELAY [A/F RELAY])


    1. Disconnect the air fuel ratio sensor connector.

    2. Remove the integration relay (A/F relay) from the engine room relay block.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      C56-2 (+B) - 1B-8 Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      C56-2 (+B) or 1B-8 - Body ground Always 10 kΩ or higher

    4. Reconnect the air fuel ratio sensor connector.

    5. Reinstall the integration relay.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    GO TO ECM POWER SOURCE CIRCUIT Click here