06/09/2026
DESCRIPTION: Oxygen Sensor Heater Control Circuit High/Low
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); DTC P0051: Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 2 Sensor 1); DTC P0052: Oxygen (A/F) Sensor Heater Control Circuit High (Bank 2 Sensor 1):
DESCRIPTION
HINT
👉 Although the DTC titles include 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 air fuel ratio sensor generates voltage that corresponds to the actual air fuel ratio. This sensor voltage 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 time. If the air fuel ratio sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.
The air fuel ratio sensor is the planar type and is integrated with a 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 narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, therefore the 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.
Value changes inside the ECM. Since the air fuel ratio sensor is the current output element, the current is converted to a voltage inside the ECM. Any measurements taken at the air fuel ratio sensor or ECM connectors will show a constant voltage.
HINT :
👉 When any of these DTCs are set, 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.
👉 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.
P0031 P0051
DTC Detection Condition:
Air fuel ratio sensor heater (bank 1, 2 sensor 1) current less than 0.8 A
(1 trip detection logic)
Trouble Area:
👉 Open in air fuel ratio sensor heater (bank 1, 2 sensor 1) circuit
👉 Air fuel ratio sensor heater (bank 1, 2 sensor 1)
👉 A/F fuse
👉 Engine room junction block assembly (A/F relay)
👉 ECM
DTC No.
P0032 P0052
DTC Detection Condition:
Air fuel ratio sensor heater (bank 1, 2 sensor 1) current fail
(1 trip detection logic)
Trouble Area:
👉 Short in air fuel ratio sensor heater (bank 1, 2 sensor 1) circuit
👉 Air fuel ratio sensor heater (bank 1, 2 sensor 1)
👉 A/F fuse
👉 Engine room junction block assembly (A/F relay)
👉 ECM.
HINT:
👉 Bank 1 refers to the bank that includes cylinder No. 1.
👉 Bank 2 refers to the bank that does not include cylinder No. 1.
👉 Sensor 1 refers to the sensor closest to the engine assembly.
👉 Sensor 2 refers to the sensor farthest away from the engine assembly
