Circuit Description
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.
Refer to CIRCUIT DESCRIPTION under DTC P2195: OXYGEN (A/F) SENSOR SIGNAL STUCK LEAN (BANK 1 SENSOR 1), DTC P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK RICH (BANK 1 SENSOR 1).
HINT:
The ECM provides a pulse width modulated control circuit to adjust current through the heater. The A/F sensor heater circuit uses a relay on the +B side of the circuit.