Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

Engine. Camry. Acv40 Gsv40
2Az-Fe Engine Control System. Camry. Acv40 Gsv40

DESCRIPTION

MONITOR DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE)

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

INSPECT ENGINE ROOM J/B (EFI RELAY, EFI MAIN FUSE)

CHECK HARNESS AND CONNECTOR (A/F SENSOR - EFI RELAY)

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

CHECK WHETHER DTC OUTPUT RECURS

DTC P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

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


DESCRIPTION

Refer to DTC P2195 (Link).
HINT:
  1. Although the DTC titles say oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
  2. Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
  3. When either of these DTCs is set, 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 ignition switch is turned off.

  4. The ECM provides a pulse width modulated signal to the 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.


    Camry. Acv40 Gsv40.2Az-Fe Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)


DTC No.
DTC Detection Condition
Trouble Area
P0031
Air-Fuel Ratio (A/F) sensor heater current less than 0.8 A
(1 trip detection logic)
  1. Open in A/F sensor heater circuit
  2. A/F sensor heater (sensor 1)
  3. Engine room J/B (EFI relay)
  4. ECM
P0032
Air-Fuel Ratio (A/F) sensor heater current more than 10 A
(1 trip detection logic)
  1. Short in A/F sensor heater circuit
  2. A/F sensor heater (sensor 1)
  3. Engine room J/B (EFI relay)
  4. ECM

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 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 sets a DTC.
Example:
The ECM sets DTC P0032 when the current in the A/F sensor heater is more than 10 A. Conversely, when the heater current is less than 0.8 A, DTC P0031 is set.

WIRING DIAGRAM

Refer to DTC P2195 (CAMRY_ACV40 RM000000WC401HX_07.html).

INSPECTION PROCEDURE

HINT:
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.
1.INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE)


    Camry. Acv40 Gsv40.2Az-Fe Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Disconnect the C15 A/F sensor connector.

  1. Measure the resistance between the terminals of the A/F sensor connector.

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

  1. Reconnect the A/F sensor connector.



NG
REPLACE AIR-FUEL RATIO SENSOR
OK


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


    Camry. Acv40 Gsv40.2Az-Fe Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Disconnect the C15 A/F sensor connector.

  1. Turn the ignition switch to the ON position.

  1. Measure the voltage between the terminal of the A/F sensor connector and body ground.

    Standard voltage:
    Tester Connection
    		Specified Condition
    +B (C15-2) - Body ground
    		9 to 14 V

  1. Reconnect the A/F sensor connector.



OK
Go to step 5
NG


3.INSPECT ENGINE ROOM J/B (EFI RELAY, EFI MAIN FUSE)


    Camry. Acv40 Gsv40.2Az-Fe Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Inspect the EFI MAIN fuse.

    1. Remove the EFI MAIN fuse from the engine room J/B.

    2. Measure the EFI MAIN fuse resistance.

      Standard resistance:
      Below 1 Ω

    3. Reinstall the EFI MAIN fuse.

  1. Inspect the EFI relay.

    1. Remove the engine room J/B from the engine room R/B.

    2. Measure the EFI relay resistance.

      Standard resistance:
      Tester Connection
      		Specified Condition
      1E-7 - 1E-12
      		10 kΩ or higher
      Below 1 Ω
      (Apply battery voltage between terminals 1E-9 and 1E-11)

    3. Reinstall the engine room J/B.



NG
REPLACE ENGINE ROOM J/B AND/OR EFI MAIN FUSE
OK


4.CHECK HARNESS AND CONNECTOR (A/F SENSOR - EFI RELAY)


    Camry. Acv40 Gsv40.2Az-Fe Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Disconnect the C15 A/F sensor connector.

  1. Remove the engine room J/B from the engine room R/B.

  1. Disconnect the 1E engine room J/B connector.

  1. Measure the resistance between the terminals.

    Standard resistance (Check for open):
    Tester Connection
    		Specified Condition
    +B (C15-2) - Engine room J/B (1E-7)
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connection
    		Specified Condition
    +B (C15-2) or Engine room J/B (1E-7) - Body ground
    		10 kΩ or higher

  1. Reconnect the A/F sensor connector.

  1. Reconnect the engine room J/B connector.

  1. Reinstall the engine room J/B.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

CHECK ECM POWER SOURCE CIRCUIT

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


    Camry. Acv40 Gsv40.2Az-Fe Engine Control System.Sfi System. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Disconnect the C15 A/F sensor connector.

  1. Disconnect the C24 ECM connector.

  1. Measure the resistance between the terminals of the wire harness side connectors.

    Standard resistance (Check for open):
    Tester Connection
    		Specified Condition
    HA1A (C15-1) - HA1A (C24-109)
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connection
    		Specified Condition
    HA1A (C15-1) or HA1A (C24-109) - Body ground
    		10 kΩ or higher

  1. Reconnect the A/F sensor connector.

  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


6.CHECK WHETHER DTC OUTPUT RECURS

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to the ON position.

  1. Turn the tester on.

  1. Clear the DTCs (CAMRY_ACV40 RM000000PDK01RX.html).

  1. Start the engine.

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

  1. Select the following menu items: Powertrain / Engine and ECT / DTC.

  1. Read the DTCs.


Result:

Display (DTC Output)
Proceed to
No output
A
P0031 or P0032
B


B
REPLACE ECM
A

CHECK FOR INTERMITTENT PROBLEMS