Circuit Description

WARNING: This page is about a different car, the 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.

Heated oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. ECM uses input signal to determine fuel injection system operation. DTC P0141 applies to heated oxygen sensor (bank No. 1 sensor 2). DTC P0161 applies to heated oxygen sensor (bank No. 2 sensor 2). Heated oxygen sensors are located on exhaust manifold below catalytic converters. Heated oxygen sensor for cylinders No. 1 and 4 is referred to as bank No. 1 sensor No. 2. Heated oxygen sensor for cylinders No. 2 and 3 is referred to as bank No. 2 sensor No. 2. In testing procedure, these heated oxygen sensors are referred to as heated oxygen sensor No. 2. DTC is set when heated oxygen sensor heater current draw exceeds 2 amps, or heated oxygen sensor heater current draw is .2 amp or less when heater operates. If DTC P0141 or DTC P0161 exists, ECM will operate in fail-safe mode and turn off heater on oxygen sensor. Possible causes are:

Heated oxygen sensor No. 2 heater circuit is open or shorted.
Defective heated oxygen sensor No. 2 heater.
Defective ECM.