SFI SYSTEM (w/ EGR 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

Tech Tips

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

The air fuel ratio sensor generates voltage* that corresponds to the actual air fuel ratio. This sensor voltage is used to provide the ECM with feedback so that it can control the air fuel ratio. The ECM determines the deviation from the stoichiometric air fuel ratio level, and regulates the fuel injection time. If the air fuel ratio sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.

The air fuel ratio sensor is the planar type and is integrated with a heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, therefore the sensor activation is accelerated.

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a three way catalytic converter is used. For the most efficient use of the three way catalytic converter, the air fuel ratio must be precisely controlled so that it is always close to the stoichiometric level.

*: Value changes inside the ECM. Since the air fuel ratio sensor is the current output element, the current is converted to a voltage inside the ECM. Any measurements taken at the air fuel ratio sensor or ECM connectors will show a constant voltage.

A01NF5DE01

Tech Tips


  • When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the air fuel ratio sensor heater in fail-safe mode. Fail-safe mode continues until the power 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.

    A01ND2AE02
DTC No. DTC Detection Condition Trouble Area

P0031

P0051

Air fuel ratio sensor heater (bank 1, 2 sensor 1) current less than 0.8 A

(1 trip detection logic)

  • Open in air fuel ratio sensor heater (bank 1, 2 sensor 1) circuit

  • Air fuel ratio sensor heater (bank 1, 2 sensor 1)

  • A/F fuse

  • Engine room junction block assembly (A/F relay)

  • ECM

P0032

P0052

Air fuel ratio sensor heater (bank 1, 2 sensor 1) current fail

(1 trip detection logic)

  • Short in air fuel ratio sensor heater (bank 1, 2 sensor 1) circuit

  • Air fuel ratio sensor heater (bank 1, 2 sensor 1)

  • A/F fuse

  • Engine room junction block assembly (A/F relay)

  • ECM

P101D

P103D

Air fuel ratio sensor heater (bank 1, 2 sensor 1) current is more than the specified value while the heater is not operating

(1 trip detection logic)

 ECM

WIRING DIAGRAM

Refer to DTC P2195 Click here.

INSPECTION PROCEDURE

Note

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

Tech Tips


  • Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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.

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

    *: The No. 1 cylinder is the cylinder which is farthest from the transmission.

  • 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.

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)


    1. A01NDLWE27
      Text in Illustration
      *1 Bank 1
      *2 Bank 2
      *a

      Front view of wire harness connector

      (to Air Fuel Ratio Sensor)

      Disconnect the air fuel ratio sensor connector.

    2. Turn the power switch on (IG).

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      D20-2 (+B) - Body ground Power switch on (IG) 11 to 14 V
      D19-2 (+B) - Body ground Power switch on (IG) 11 to 14 V

    4. Reconnect the air fuel ratio sensor connector.


    NG

    CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ENGINE ROOM JUNCTION BLOCK ASSEMBLY) 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
      D20-1 (HA1A) - D1-24 (HA1A) Always Below 1 Ω
      D19-1 (HA2A) - D1-22 (HA2A) Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      D20-1 (HA1A) or D1-24 (HA1A) - Body ground Always 10 kΩ or higher
      D19-1 (HA2A) or D1-22 (HA2A) - 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 (AIR FUEL RATIO SENSOR - ECM)

    OK

    REPLACE ECM Click here

  4. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ENGINE ROOM JUNCTION BLOCK ASSEMBLY)


    1. Disconnect the air fuel ratio sensor connector.

    2. Remove the engine room junction block assembly.

    3. Disconnect the engine room junction block assembly connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      D20-2 (+B) - 3C-2 (Engine room junction block assembly) Always Below 1 Ω
      D19-2 (+B) - 3C-2 (Engine room junction block assembly) Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      D20-2 (+B) or 3C-2 (Engine room junction block assembly) - Body ground Always 10 kΩ or higher
      D19-2 (+B) or 3C-2 (Engine room junction block assembly) - Body ground Always 10 kΩ or higher

    5. Reconnect the engine room junction block assembly connector.

    6. Reinstall the engine room junction block assembly.

    7. Reconnect the air fuel ratio sensor connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - ENGINE ROOM JUNCTION BLOCK ASSEMBLY)

    OK

  5. CHECK TERMINAL VOLTAGE (ENGINE ROOM JUNCTION BLOCK ASSEMBLY)


    1. A01NH5QE08
      Text in Illustration
      *1 Engine Room Junction Block Assembly
      *a

      Front view of wire harness connector

      (to Engine Room Junction Block Assembly)

      Remove the engine room junction block assembly.

    2. Disconnect the engine room junction block assembly connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      3A-1 (Engine room junction block assembly) - Body ground Always 11 to 14 V

    4. Reconnect the engine room junction block assembly connector.

    5. Reinstall the engine room junction block assembly.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - BATTERY)

    OK

  6. CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - EFI MAIN RELAY)


    1. Remove the engine room junction block assembly.

    2. Disconnect the engine room junction block assembly connector.

    3. Remove the EFI MAIN relay from the engine room relay block.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      3C-7 (Engine room junction block assembly) - EFI MAIN relay terminal 3 Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      3C-7 (Engine room junction block assembly) or EFI MAIN relay terminal 3 - Body ground Always 10 kΩ or higher

    5. Reinstall the EFI MAIN relay.

    6. Reconnect the engine room junction assembly connector.

    7. Reinstall the engine room junction block assembly.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - EFI MAIN RELAY)

    OK

  7. CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - BODY GROUND)


    1. Remove the engine room junction block assembly.

    2. Disconnect the engine room junction block assembly connector.

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

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      3C-17 (Engine room junction block assembly) - Body ground Always Below 1 Ω

    4. Reconnect the engine room junction block assembly connector.

    5. Reinstall the engine room junction block assembly.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - BODY GROUND)

    OK

    REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY