SFI SYSTEM, Diagnostic DTC:P0031, P0032, P0051, P0052, P101D, P103D

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)
P0051 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 2 Sensor 1)
P0052 Oxygen (A/F) Sensor Heater Control Circuit High (Bank 2 Sensor 1)
P101D A/F Sensor Heater Circuit Performance Bank 1 Sensor 1 Stuck ON
P103D A/F Sensor Heater Circuit Performance Bank 2 Sensor 1 Stuck ON

DESCRIPTION

Refer to DTC P2195 Click here.

Tech Tips


  • Although the DTC titles say oxygen sensor, these DTCs relate to the Air Fuel ratio (A/F) 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 A/F 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 A/F sensor heater circuit uses a relay on the +B side of the circuit.

    A01ERWVE02
DTC Code DTC Detection Condition Trouble Area

P0031

P0051

The Air Fuel ratio (A/F) sensor heater current is below 0.8 A

(1 trip detection logic).

  • Open in Air Fuel ratio (A/F) sensor heater circuit

  • A/F sensor heater (for Sensor 1)

  • Integration relay

  • ECM

P0032

P0052

An Air Fuel ratio (A/F) sensor heater current failure

(1 trip detection logic).

  • Short in A/F sensor heater circuit

  • A/F sensor heater (for Sensor 1)

  • Integration relay

  • ECM

P101D

P103D

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

Tech Tips


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

  • Bank 2 refers to the bank that does not include the 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 ECM uses information from the Air Fuel ratio (A/F) 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 A/F 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 A/F 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 A/F sensor becomes inaccurate. As a result, the ECM is unable to regulate the air-fuel ratio properly.

When the current in the A/F sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores DTC(s).

WIRING DIAGRAM

Refer to DTC P2195 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 AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

    A01ERHXE06

    1. Disconnect the Air Fuel ratio (A/F) sensor connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      1 (HA1A) - 2 (+B) 20°C (68°F) 1.8 to 3.4 Ω
      1 (HA1A) - 4 (A1A-) Always 10 kΩ or higher
      1 (HA2A) - 2 (+B) 20°C (68°F) 1.8 to 3.4 Ω
      1 (HA2A) - 4 (A2A-) Always 10 kΩ or higher

    NG

    REPLACE AIR FUEL RATIO SENSOR Click here

    OK

  2. CHECK TERMINAL VOLTAGE (+B OF A/F SENSOR)

    A01EPOIE12

    1. Disconnect the A/F sensor connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      C47-2 (+B) - Body ground Engine switch on (IG) 11 to 14 V
      C48-2 (+B) - Body ground Engine switch on (IG) 11 to 14 V
      Result
      Result Proceed to
      NG A
      OK B

    B

    CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM) Click here

    A

  3. INSPECT INTEGRATION RELAY (A/F)


    1. Remove the integration relay from the engine room relay block.

    2. A01EN9SE04

      Inspect the A/F fuse.


      1. Remove the A/F fuse from the integration relay.

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

        Standard Resistance
        Tester Connection Condition Specified Condition
        A/F fuse Always Below 1 Ω

      3. Reinstall the A/F fuse.

    3. Inspect the integration relay (A/F).


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

        Standard Resistance
        Tester Connection Condition Specified Condition
        1C-1 - 1A-4 No battery voltage applied to terminals 1A-2 and 1A-3 10 kΩ or higher
        Battery voltage applied to terminals 1A-2 and 1A-3 Below 1 Ω

    NG

    REPLACE INTEGRATION RELAY (A/F)

    OK

  4. CHECK HARNESS AND CONNECTOR (INTEGRATION RELAY - A/F SENSOR AND BODY GROUND)

    A01EPWFE02

    1. Disconnect the A/F sensor connector.

    2. Remove the integration relay from the engine room relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      C47-2 (+B) - 1A-4 Always Below 1 Ω
      C48-2 (+B) - 1A-4 Always Below 1 Ω
      1A-2 - 1B-4 Always Below 1 Ω
      1A-3 - Body ground Always Below 1 Ω
      C47-2 (+B) or 1A-4 - Body ground Always 10 kΩ or higher
      C48-2 (+B) or 1A-4 - Body ground Always 10 kΩ or higher
      1A-2 or 1B-4 - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    CHECK ECM POWER SOURCE CIRCUIT Click here

  5. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)


    1. Disconnect the A/F sensor connector.

    2. Disconnect the ECM connector.

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

      Standard Resistance
      for LHD
      Tester Connection Condition Specified Condition
      C47-1 (HA1A) - C53-22 (HA1A) Always Below 1 Ω
      C48-1 (HA2A) - C53-20 (HA2A) Always Below 1 Ω
      C47-1 (HA1A) or C53-22 (HA1A) - Body ground Always 10 kΩ or higher
      C48-1 (HA2A) or C53-20 (HA2A) - Body ground Always 10 kΩ or higher
      for RHD
      Tester Connection Condition Specified Condition
      C47-1 (HA1A) - C54-22 (HA1A) Always Below 1 Ω
      C48-1 (HA2A) - C54-20 (HA2A) Always Below 1 Ω
      C47-1 (HA1A) or C54-22 (HA1A) - Body ground Always 10 kΩ or higher
      C48-1 (HA2A) or C54-20 (HA2A) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  6. CHECK WHETHER DTC OUTPUT RECURS


    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the 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 / DTC.

    8. Read DTCs.

      Result
      Result Proceed to
      No DTC is output A
      P0031, P0032, P0051, P0052, P101D or P103D is output B

    B

    REPLACE ECM Click here

    A

    CHECK FOR INTERMITTENT PROBLEMS Click here