Circuit Description

Heated oxygen sensors monitor exhaust gas oxygen content and deliver input signals to Engine Control Module (ECM). Heated oxygen sensors are located on exhaust manifold below catalytic converters. See Figure. Heated oxygen sensor for cylinders No. 1 and 4 is referred to as bank No. 1, sensor No. 2. ECM uses input signals to determine fuel injection system operation. DTC is set when heated oxygen sensor (bank No. 1, sensor No. 2) output voltage remains at .40 volt or more, or .50 volt or less when vehicle is driven at 25 MPH with engine at normal operating temperature. Possible causes are:

• Heated oxygen sensor (bank No. 1, sensor No. 2) circuit is open or shorted.
• Defective heated oxygen sensor (bank No. 1, sensor No. 2).