DTC P0036-12: HO2S Heater Control Circuit Bank 1 Sensor 2 Circuit Short to Battery; DTC P0036-13: A/F (O2) Heater Control Circuit Bank 1 Sensor 2 Circuit Open; DTC P102A-9E: O2 Sensor Heater Performance Bank 1 Sensor 2 Stuck On [10/2022 - 11/2023]: Description

The air fuel ratio sensor (sensor 2) 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 2) malfunctions, the ECM is unable to control the air fuel ratio accurately.

The air fuel ratio sensor (sensor 2) is a cup type sensor and uses a zirconia element for the sensor element. The zirconium element is made of platinum coated zirconium and includes an integrated heating element. The inner surface of the zirconia element is exposed to the outside air and the outer surface of it is exposed to the exhaust gas. The zirconia element generates a voltage according to the oxygen concentration of the exhaust gas and outside air. The air fuel ratio sensor (sensor 2) becomes very efficient when heated. When the exhaust gas temperature is low, the sensor does not generate useful voltage signals without supplementary heating. Therefore, the air fuel ratio sensor (sensor 2) includes a heater to heat the zirconia element.

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 air fuel ratio.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT: 

• When any of these DTCs are stored, the ECM enters fail-safe mode. The ECM turns off the air fuel ratio sensor (sensor 2) 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 2).
• The ECM has a pulse width modulated control circuit to adjust the current through the heater. The air fuel ratio sensor (sensor 2) heater circuit uses a relay on the +B side of the circuit.

  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002