DTC P0031: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 1); DTC P0032: Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 1): Description

HINT:

Although the DTC titles say oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
When any of these DTCs are set, 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 off.
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.

Fig 1: Sensor 1 System Reference Diagram
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

DTC TROUBLE DETECTION CHART

DTC No.	DTC Detection Condition	Trouble Area
P0031	A/F sensor heater current less than 0.8 A (1 trip detection logic)	Open in A/F sensor heater circuit A/F sensor heater EFI relay ECM
P0032	A/F sensor heater current more than 10 A (1 trip detection logic)	Short in A/F sensor heater circuit A/F sensor heater EFI relay ECM