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. Heated oxygen sensors are located on exhaust manifold below catalytic converters. ECM uses input signal to determine fuel injection system operation. Heated oxygen sensors include a heater. DTC P0136 applies to heated oxygen sensor (bank No. 1 sensor 2). DTC P0156 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 voltage remains at .4 volt or more, or .5 volt or less during vehicle operation (25 MPH or more), once engine is at normal operating temperature. Possible cause is:

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