1Nz-Fe Engine Control. Dtc P0031 Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

When any of these DTCs is stored, 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 ignition switch is turned off.
Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.
Sensor 1 refers to the sensor mounted in front of the three-way catalytic converter and located near the engine assembly.

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.

DTC No.	DTC Detection Condition	Trouble Area
P0031	Air fuel ratio sensor heater current is below 0.8 A, even when the air fuel ratio sensor heater duty cycle is 30% or more. (1 trip detection logic)	Open in air fuel ratio sensor heater circuit Air fuel ratio sensor (bank 1 sensor 1) ECM
P0032	Air fuel ratio sensor heater current reaches the high limit (Hybrid IC high current limiter port "Fail"). (1 trip detection logic)	Short in air fuel ratio sensor heater circuit Air fuel ratio sensor (bank 1 sensor 1) ECM
P101D	The heater current is higher than the specified value while the heater is not operating (1 trip detection logic).	ECM

HINT:

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 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 to purify the exhaust gases.
The air fuel ratio 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 air fuel ratio 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 air fuel ratio sensor becomes inaccurate. As a result, the ECM is unable to regulate the air fuel ratio properly.
When the current in the air fuel ratio sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC.

MONITOR STRATEGY

Related DTCs	P0031: Air Fuel Ratio Sensor Heater Open/Short (Low Electrical Current) P0032: Air Fuel Ratio Sensor Heater Open/Short (High Electrical Current) P101D: Air Fuel Ratio Sensor Heater Performance
Required Sensors/Components (Main)	Air fuel ratio sensor heater
Required Sensors/Components (Related)	-
Frequency of Operation	Continuous
Duration	10 seconds: P0031 10.24 seconds: P0032 1 second: P101D
MIL Operation	Immediate
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

P0031:
Monitor runs whenever following DTCs not present	None
Battery voltage	10.5 V or more
Time after heater ON	5 seconds or more
Active heater OFF control	Not operating
Active heater ON control	Not operating
Heater output duty	30% or more
A/F sensor heater performance fail (P101D)	Not detected

P0032:
Monitor runs whenever following DTCs not present	None
Battery voltage	10.5 V or more
Time after heater ON	5 seconds or more
Active heater OFF control	Not operating
Active heater ON control	Not operating
Heater output duty	More than 0%

P101D:
Monitor runs whenever following DTCs not present	None
Battery voltage	10.5 V or more
Time after heater ON	5 seconds or more
Air fuel ratio sensor heater duty-cycle ratio	10 to 60%
Air fuel ratio sensor heater ON current	0.8 A or more
Active heater OFF control	Not operating
Active heater ON control	Not operating
Air fuel ratio sensor heater range check low current fail (P0031)	Not detected

TYPICAL MALFUNCTION THRESHOLDS

P0031:
Air fuel ratio sensor heater ON current	Less than 0.8 A

P0032:
All of the following conditions are met	-
1. Air fuel ratio sensor heater output	ON
2. Hybrid IC high current limiter port	Fail

P101D:
Air fuel ratio sensor heater OFF current	More than 11 A
Hybrid IC high current limiter port	Fail

COMPONENT OPERATING RANGE

P0031:
Air fuel ratio sensor heater ON current	0.8 A or more

P0032:
All of the following conditions are met	-
1. Air fuel ratio sensor heater output	ON
2. Hybrid IC high current limiter monitor input	Pass

P101D:
Air fuel ratio sensor heater ON current	11 A or less

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)

Connect the Techstream to the DLC3.
Turn the ignition switch to ON and turn the Techstream on.
Clear DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the ignition switch off and wait for at least 30 seconds.
Turn the ignition switch to ON and turn the Techstream on [A].
Start the engine and idle it for 5 minutes or more [B].
With the vehicle stationary, depress the accelerator pedal and maintain an engine speed of 3000 rpm for 1 minute [C].
Idle the engine for 5 minutes or more [D].
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [E].
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.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTC: P0031, P0032, or P101D.

Check the DTC judgment result.

Techstream Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

HINT:

If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.
If the judgment result shows INCOMPLETE or N/A, perform steps [B] through [E] again.

If no pending DTC is output, perform a universal trip and check for permanent DTCs (YARIS_NCP93 RM000000PDK0T5X.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

INSPECTION PROCEDURE

NOTICE:

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

HINT:

Refer to "Data List / Active Test" [A/F Heater Duty #1] (YARIS_NCP93 RM000000SXS05AX.html).
Sensor 1 refers to the sensor closest to the engine assembly.
Sensor 2 refers to the sensor farthest away from the engine assembly.
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.
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 RM000000WBY0F2X_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)

Inspect the air fuel ratio sensor (YARIS_NCP93 RM000003VIJ00FX.html).
HINT:
Perform "Inspection After Repair" after replacing the air fuel ratio sensor (YARIS_NCP93 RM000004NJD006X.html).

REPLACE AIR FUEL RATIO SENSOR (YARIS_NCP93 RM000003VIL00HX.html)

OK

2.INSPECT TERMINAL VOLTAGE (POWER SOURCE OF AIR FUEL RATIO SENSOR)

Disconnect the air fuel ratio sensor connector.

Turn the ignition switch to ON.

Measure the voltage according to the value(s) in the table below.
Standard Voltage:
Tester Connection
Switch Condition
Specified Condition
C56-2 (+B) - Body ground
Ignition switch ON
11 to 14 V
Text in Illustration
*a
Front view of wire harness connector
(to Air Fuel Ratio Sensor)

Text in Illustration
*a	Front view of wire harness connector (to Air Fuel Ratio Sensor)

Go to step 5

OK

3.CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)

Disconnect the air fuel ratio sensor connector.

Disconnect the ECM connector.

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

Standard Resistance:

Tester Connection
Condition
Specified Condition
C56-1 (HA1A) - C51-23 (HA1A)
Always
Below 1 Ω
C56-1 (HA1A) or C51-23 (HA1A) - Body ground
Always
10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.CHECK WHETHER DTC OUTPUT RECURS (DTC P0031, P0032 OR P101D)

Connect the Techstream to the DLC3.

Turn the ignition switch to ON.

Turn the Techstream on.

Clear the DTCs (YARIS_NCP93 RM000000PDK0T5X.html).

Turn the ignition switch off and wait for at least 30 seconds.

Turn the ignition switch to ON.

Turn the Techstream on.

Start the engine.

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

Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.
Result
Result
Proceed to
DTC is not output
A
DTC P0031, P0032 or P101D is output
B

Result
Result	Proceed to
DTC is not output	A
DTC P0031, P0032 or P101D is output	B

REPLACE ECM (YARIS_NCP93 RM000001CN002IX.html)

CHECK FOR INTERMITTENT PROBLEMS (YARIS_NCP93 RM000000PDQ0Q2X.html)

5.CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - NO. 1 INTEGRATION RELAY)

Disconnect the air fuel ratio sensor connector.

Remove the No. 1 integration relay from the engine room relay block.

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

Standard Resistance:

Tester Connection
Condition
Specified Condition
C56-2 (+B) - 1E-4
Always
Below 1 Ω
C56-2 (+B) or 1E-4 - Body ground
Always
10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK ECM POWER SOURCE CIRCUIT (YARIS_NCP93 RM000001F7102NX.html)

Tester Connection	Switch Condition	Specified Condition
C56-2 (+B) - Body ground	Ignition switch ON	11 to 14 V

Tester Connection	Condition	Specified Condition
C56-1 (HA1A) - C51-23 (HA1A)	Always	Below 1 Ω
C56-1 (HA1A) or C51-23 (HA1A) - Body ground	Always	10 kΩ or higher