M20A-FKS (ENGINE CONTROL): SFI SYSTEM: P003012,P003013,P101A9E; HO2S Heater Control Bank 1 Sensor 1 Circuit Short to Battery; 2023 - 2025 MY Corolla Corolla Hatchback [03/2023

The air fuel ratio sensor (sensor 1) generates current that corresponds to the actual air fuel ratio. This sensor current 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 duration. If the air fuel ratio sensor (sensor 1) malfunctions, the ECM is unable to control the air fuel ratio accurately.

The air fuel ratio sensor (sensor 1) is a planar type sensor and integrated with the 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 a narrow type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, therefore 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.

for K120

for K121

HINT:

When any of these DTCs are stored, the ECM enters fail-safe mode. The ECM turns off the air fuel ratio sensor (sensor 1) 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).
The ECM has a pulse width modulated control circuit to adjust the current through the heater. The air fuel ratio sensor (sensor 1) heater circuit uses a relay on the +B side of the circuit.

MONITOR DESCRIPTION

The ECM uses information from the air fuel ratio sensor (sensor 1) 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 (sensor 1) 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 (sensor 1) is more efficient when heated. When the exhaust gas temperature is low, the sensor cannot generate useful current 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 (sensor 1) becomes inaccurate. As a result, the ECM is unable to regulate the air fuel ratio properly.

Air Fuel Ratio Sensor (sensor 1) Heater Range Check (P003012 and P003013):

The ECM monitors the current applied to the air fuel ratio sensor (sensor 1) heater to check the heater for malfunctions.
If the heater current is outside the normal range, the signal transmitted by the air fuel ratio sensor (sensor 1) becomes inaccurate. When the current in the air fuel ratio sensor (sensor 1) heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC.

Air Fuel Ratio Sensor (sensor 1) Heater Performance (P101A9E):

When the current in the air fuel ratio sensor (sensor 1) heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC. (for K120)
When the air fuel ratio sensor (sensor 1) heater terminal voltage is the specified value or less while the heater is not operating, the ECM determines that there is a malfunction in the sensor heater and stores DTC. (for K121)

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

P0031

P0032

P101D

TYPICAL MALFUNCTION THRESHOLDS

P0031

P0032 (for K120)

P0032 (for K121)

P101D (for K120)

P101D (for K121)

CONFIRMATION DRIVING PATTERN

HINT:

After repair has been completed, clear the DTC and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.
Click here
When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.
Click here

Connect the Techstream to the DLC3.
Turn the ignition switch to ON.
Turn the Techstream on.
Clear the 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 [A].
Turn the Techstream on.
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 / Trouble Codes [E].
Read the pending DTCs.
HINT:
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine / Utility / All Readiness.
Input the DTC: P003012, P003013 or P101A9E.

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

HINT:

If the judgment result is NORMAL, the system is normal.
If the judgment result is ABNORMAL, the system has a malfunction.
If the judgment result is INCOMPLETE, perform steps [B] through [E] again.
[A] to [E]: Normal judgment procedure.
The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.
When clearing the permanent DTCs, do not disconnect the cable from the battery terminal or attempt to clear the DTCs during this procedure, as doing so will clear the universal trip and normal judgment histories.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

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

HINT:

Refer to "Data List / Active Test" [A/F (O2) Sensor Heater Duty Ratio B1S1].
Click here
Sensor 1 refers to the sensor closest to the engine assembly.
Sensor 2 refers to the sensor farthest away from the engine assembly.
Change the fuel injection volume using the Control the Injection Volume for A/F Sensor function provided in the Active Test and monitor the air fuel ratio sensor (sensor 1) output current (Click here ). If the sensor output current does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.
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.

PROCEDURE

Perform "Inspection After Repair" after replacing the air fuel ratio sensor (sensor 1).

Powertrain > Engine > Clear DTCs

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

Powertrain > Engine > Trouble Codes

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