Circuit Description

The oxygen sensor monitor exhaust gas oxygen content and delivers an input signal to ECM. The ECM uses input signal to determine fuel injection system operation. Sensors include heater. Code is set when sensor does not output a rich condition once engine is at normal operating temperature, engine speed is 1500 RPM or more, and vehicle speed is at least 25 MPH for at least 2 minutes. Possible causes are:

• Open or short in oxygen sensor circuit.
• Heated oxygen sensor malfunction.