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): Notes
WARNING: This page is about a different car, the 2004 Toyota RAV4. However, it is still accessible from the selected car via links, so may be relevant.
HINT:
Although the title (DTC description) says "oxygen sensor", this DTC is related to the "A/F sensor".