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

Engine Hybrid System. Yaris. Ncp93, 131
1Nz-Fe Engine Control. Yaris. Ncp93, 131

DESCRIPTION

MONITOR DESCRIPTION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

COMPONENT OPERATING RANGE

CONFIRMATION DRIVING PATTERN

WIRING DIAGRAM

INSPECTION PROCEDURE

INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE)

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

INSPECT INTEGRATION RELAY (EFI RELAY)

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

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

CHECK WHETHER DTC OUTPUT RECURS (DTC P0031 OR P0032)

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 (YARIS_NCP93 RM000000WC40K6X_01.html).
HINT:
  1. Although the DTC titles say the 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 are 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 ignition switch is turned to OFF.

  4. 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.


    Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). 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. Integration relay (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. Integration relay (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 stores a DTC.
Example:
The ECM stores 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 stored.

MONITOR STRATEGY


Related DTCs
P0031: A/F sensor heater open/short (Low electrical current)
P0032: A/F sensor heater open/short (High electrical current)
Required Sensors/Components (Main)
A/F sensor heater
Required Sensors/Components (Related)
-
Frequency of Operation
Continuous
Duration
10 seconds
MIL Operation
Immediate
Sequence of Operation
None

TYPICAL ENABLING CONDITIONS


All:
Monitor runs whenever following DTCs not present
None

P0031:
Battery voltage
10.5 V or more
A/F sensor heater duty-cycle
50% or more
Time after engine start
10 seconds or more

P0032:
Time after engine start
10 seconds or more

TYPICAL MALFUNCTION THRESHOLDS


P0031:
A/F sensor heater current
Less than 0.8 A

P0032:
A/F sensor heater current
More than 10 A

COMPONENT OPERATING RANGE


A/F sensor heater current
0.9 to 9.9 A

CONFIRMATION DRIVING PATTERN


Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Connect the Techstream to the DLC3.
  2. Turn the ignition switch to ON and turn the Techstream on.
  3. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
  4. Turn the ignition switch off and wait for at least 30 seconds.
  5. Turn the ignition switch to ON and turn the Techstream on [A].
  6. Start the engine and idle it for 5 minutes or more [B].
  7. With the vehicle stationary, depress the accelerator pedal and maintain an engine speed of 3000 rpm for 1 minute [C].
  8. Idle the engine for 5 minutes or more [D].
  9. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [E].
  10. Read pending DTCs.
    HINT:
    1. If a pending DTC is output, the system is malfunctioning.
    2. If a pending DTC is not output, perform the following procedure.
  11. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
  12. Input the DTC: P0031 or P0032.
  13. Check the DTC judgment result.

    Techstream Display
    		Description
    NORMAL
    1. DTC judgment completed
    2. System normal
    ABNORMAL
    1. DTC judgment completed
    2. System abnormal
    INCOMPLETE
    1. DTC judgment not completed
    2. Perform driving pattern after confirming DTC enabling conditions
    N/A
    1. Unable to perform DTC judgment
    2. Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit
    HINT:
    1. If the judgment result shows NORMAL, the system is normal.
    2. If the judgment result shows ABNORMAL, the system has a malfunction.
  14. If the judgment result shows INCOMPLETE or N/A, perform steps [B] through [E] again.
  15. If no pending DTC is output, perform a universal trip and check for permanent DTCs (YARIS_NCP93 RM000000PDK0QGX.html).
    HINT:
    1. If a permanent DTC is output, the system is malfunctioning.
    2. If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

Refer to DTC P2195 (YARIS_NCP93 RM000000WC40K6X_07.html).

INSPECTION PROCEDURE

NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.
HINT:
  1. Read freeze frame data using the Techstream. 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.
  2. Refer to "Data List / Active Test" [A/F Heater Duty #1] (YARIS_NCP93 RM000000PDN0J9X.html).
  3. Sensor 1 refers to the sensor closest to the engine assembly.
  4. Sensor 2 refers to the sensor farthest away from the engine assembly.
  5. Change the fuel injection volume using the Control the Injection Volume function provided in the Active Test and monitor the air fuel ratio sensor output voltage (YARIS_NCP93 RM000000TEO09JX_10.html). If the sensor output voltage does not change (almost no reaction) while performing the Active test, the sensor may be malfunctioning.
1.INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE)
Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Disconnect the C23 A/F sensor connector.

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

    Standard resistance:
    Tester Connections
    		Specified Conditions
    HA1A (1) - +B (2)
    		1.8 Ω 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 (YARIS_NCP93 RM000001CKA00YX.html)
OK


2.CHECK TERMINAL VOLTAGE (+B OF A/F SENSOR)
Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Disconnect the C23 A/F sensor connector.

  1. Turn the ignition switch to ON.

  1. Measure the voltage between the terminals of the C23 A/F sensor connector and body ground.

    Standard voltage:
    Tester Connections
    		Specified Conditions
    +B (C23-2) - Body ground
    		11 to 14 V
    Result
    Result
    		Proceed to
    NG
    		A
    OK
    		B

  1. Reconnect the A/F sensor connector.



B
Go to step 5
A


3.INSPECT INTEGRATION RELAY (EFI RELAY)
Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

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

  1. Inspect the EFI fuse.

    1. Remove the EFI fuse from the integration relay.

    2. Measure the EFI fuse resistance.

      Standard resistance:
      Below 1 Ω

    3. Reinstall the EFI fuse.

  1. Inspect the EFI relay.

    1. Measure the EFI relay resistance.

      Standard resistance:
      Tester Connections
      		Specified Conditions
      1C-1 - 1A-4
      		10 kΩ or higher
      Below 1 Ω
      (Apply battery voltage between terminals 1A-2 and 1A-3)

  1. Reinstall the integration relay.



NG
REPLACE INTEGRATION RELAY
OK


4.CHECK HARNESS AND CONNECTOR (A/F SENSOR - EFI RELAY)
Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Disconnect the C23 A/F sensor connector.

  1. Remove the integration relay from the engine room Relay Block (R/B).

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    +B (C23-2) - Engine room R/B (1A-4)
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    +B (C23-2) or Engine room
    R/B (1A-4) - Body ground
    		10 kΩ or higher

  1. Reconnect the A/F sensor connector.

  1. Reinstall the integration relay.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

CHECK ECM POWER SOURCE CIRCUIT (YARIS_NCP93 RM000001DN805UX.html)

5.CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)
Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

  1. Disconnect the C23 A/F sensor connector.

  1. Disconnect the C20 ECM connector.

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    HA1A (C23-1) - HA1A (C20-109)
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    HA1A (C23-1) or HA1A (C20-109) - 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 (DTC P0031 OR P0032)

  1. Connect the Techstream to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the Techstream on.

  1. Clear DTCs (YARIS_NCP93 RM000000PDK0QGX.html).

  1. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

  1. Read DTCs.


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


B
REPLACE ECM (YARIS_NCP93 RM000001CN002AX.html)
A

CHECK FOR INTERMITTENT PROBLEMS (YARIS_NCP93 RM000000PDQ0NOX.html)