ECD 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

Tech Tips


  • For more information on the air fuel ratio sensor and TOYOTA D-CAT*1, refer to the following procedures Click here.

  • This DTC is related to the air fuel ratio sensor, although the caption is the oxygen sensor.


    • *1: Diesel Clean Advanced Technology.

The air fuel ratio sensor outputs a voltage*2 that is proportional to the air fuel ratio. The air fuel ratio sensor output voltage is used to control the air fuel ratio mixture.

The air fuel ratio sensor is located after the Diesel Particulate-NOx Reduction (DPNR) catalyst. This sensor has been developed based on the structure and technology of the air fuel ratio sensor that is used for gasoline engines. The cover for the sensor electrode has been modified to suit its application in a diesel engine. This change allows the sensor to function effectively in this TOYOTA D-CAT type diesel engine, and it also avoids problems with sensor temperature and particulate matter (PM).

In order to reduce both PM and nitrogen oxides (NOx), the ECM adjusts the air-fuel ratio to a value slightly richer than that which would otherwise be used (note that this mixture is still leaner than the stoichiometric air fuel ratio). The ECM controls these adjustments on signals from the air fuel ratio sensor.

When the ECM performs PM forced regeneration (cleaning) by adding fuel using the exhaust fuel addition injector, the air fuel ratio sensor feedback is used to ensure that an appropriate air fuel ratio is maintained.

*2: This voltage change occurs only inside the ECM. It is not possible to measure this voltage at the sensor. The GTS can be used to monitor this voltage.

A00YX42E05

Tech Tips

The ECM provides a pulse width modulated control circuit to adjust current through the heater. The air fuel ratio sensor heater circuit uses a relay on the +B side of the circuit.

A00YSSNE03
DTC No. Detection Item DTC Detection Condition Trouble Area MIL Memory
P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

Air fuel ratio sensor heater current is 0.8 A or less when the heater operates for 4 seconds.

(1 trip detection logic)

  • Open in air fuel ratio sensor heater circuit

  • Air fuel ratio sensor heater

  • ECM

 Comes on DTC stored
P0032 Oxygen (A/F) Sensor Heater Control Circuit High (Bank 1 Sensor 1)

Air fuel ratio sensor heater current is 0.8 A or more when the heater does not operate for 4 seconds.

(1 trip detection logic)

  • Short in air fuel ratio sensor heater circuit

  • Air fuel ratio sensor heater

  • ECM

 Comes on DTC stored
Related Data List
DTC No. Data List
P0031

  • AFS Voltage B1S1

  • AF Lambda B1S1

  • Exhaust Temperature B1S1
P0032

MONITOR DESCRIPTION

The inner surface of the air fuel ratio sensor element is exposed to outside air. The outer surface of the sensor element is exposed to exhaust gases. 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 of the exhaust and the outside air. The platinum coating amplifies the voltage generation. When heated, the sensor becomes very efficient. If the temperature of the exhaust is low without supplemental heating, the sensor will not generate useful voltage signals. The ECM controls the heating by using a duty-cycle to regulate the average current in the heater element. If the heater current is out of the normal range, the output signals of the sensor are inaccurate and the ECM cannot regulate the air fuel ratio properly. When the heater current is out of the normal operating range, the ECM interprets this as a malfunction and stores a DTC.

CONFIRMATION DRIVING PATTERN

DTC No. DTC Detection Drive Pattern
P0031

  • Drive the vehicle at 50 km/h (30 mph) or more for a total of 300 seconds or more.

  • Check that "Exhaust Temperature B1S1" displays 200°C (392°F) or higher using the GTS.
P0032 Ignition switch ON for 5 seconds

WIRING DIAGRAM

A00YXPIE01

CAUTION / NOTICE / HINT

Note


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

  • After replacing the ECM, the new ECM needs registration (Click here ) and initialization Click here.

PROCEDURE


  1. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)


    1. Inspect the air fuel ratio sensor.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE AIR FUEL RATIO SENSOR Click here

    OK

  2. CHECK TERMINAL VOLTAGE (AIR FUEL RATIO SENSOR HEATER VOLTAGE)


    1. A00YWLIC04
      *a

      Front view of wire harness connector

      (to Air Fuel Ratio Sensor)

      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 Condition Specified Condition
      B8-2 (+B) - Body ground Ignition switch ON 11 to 14 V
      Result
      Proceed to
      OK
      NG

    NG

    CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - EFI-MAIN NO. 2 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
      B8-1 (HAF2) - B76-104 (HAF2) Always Below 1 Ω
      B8-1 (HAF2) or B76-104 (HAF2) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    GO TO STEP 11 Click here

    OK

  4. REPLACE ECM


    1. Replace the ECM.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 12 Click here

  5. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - EFI-MAIN NO. 2 RELAY)


    1. Disconnect the air fuel ratio sensor connector.

    2. Remove the EFI-MAIN NO. 2 relay from the engine room relay block and junction block assembly.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      B8-2 (+B) - 3 (EFI-MAIN NO. 2 relay) Always Below 1 Ω
      B8-2 (+B) or 3 (EFI-MAIN NO. 2 relay) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR Click here

    OK

  6. INSPECT EFI-MAIN NO. 2 RELAY


    1. Inspect the EFI-MAIN NO. 2 relay.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE EFI-MAIN NO. 2 RELAY Click here

    OK

  7. CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 2 RELAY - ECM)


    1. Remove the EFI-MAIN NO. 2 relay from the engine room relay block and junction block assembly.

    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
      1 (EFI-MAIN NO. 2 relay) - A61-45 (MREL) Always Below 1 Ω
      1 (EFI-MAIN NO. 2 relay) or A61-45 (MREL) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    GO TO STEP 11 Click here

    OK

  8. CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 2 RELAY - BODY GROUND)


    1. Remove the EFI-MAIN NO. 2 relay from the engine room relay block and junction block assembly.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      2 (EFI-MAIN NO. 2 relay) - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    GO TO STEP 11 Click here

    OK

  9. REPAIR OR REPLACE HARNESS OR CONNECTOR (EFI-MAIN NO. 2 RELAY - BATTERY)


    1. Repair or replace harness or connector.

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 12 Click here

  10. REPLACE EFI-MAIN NO. 2 RELAY


    1. Replace the EFI-MAIN NO. 2 relay.

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 12 Click here

  11. REPAIR OR REPLACE HARNESS OR CONNECTOR


    1. Repair or replace harness or connector.

      Result
      Proceed to
      NEXT

    NEXT

  12. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Clear the DTCs.


      Powertrain > Engine > Clear DTCs

    5. Turn the ignition switch off for 30 seconds or more.

    6. Turn the ignition switch to ON.

    7. Turn the GTS on.

    8. Drive the vehicle at 50 km/h (30 mph) or higher for a total of 300 seconds or more.

      Tech Tips

      "Exhaust Temperature B1S1" on the GTS screen should be 200°C (392°F) or higher.

    9. Confirm that the DTC is not output again.

      Tech Tips

      Perform the following procedure using the GTS to determine whether or not the DTC judgment has been carried out.


      1. Enter the following menus: Powertrain / Engine / Utility / All Readiness.


        Powertrain > Engine > Utility
        Tester Display
        All Readiness

      2. Input DTC P0031 and/or P0032.

      3. Check that STATUS is NORMAL.

        Tech Tips


        • If STATUS is NORMAL, DTC judgment is complete and the system is determined to be normal.

        • If STATUS is INCOMPLETE or N/A, DTC judgment is incomplete. Drive the vehicle at 50 km/h (30 mph) or higher for a total of 300 seconds or more again.

      Result
      Proceed to
      NEXT

    NEXT

    END

  13. REPLACE AIR FUEL RATIO SENSOR


    1. Replace the air fuel ratio sensor.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 12 Click here