Circuit Description

The Air/Fuel Ratio Sensor (AFS) monitors exhaust gas oxygen content and delivers an input signal to ECM. The ECM uses input signal to control air/fuel ratio. Sensor includes a heater. AFS is located in exhaust pipe. DTC is set when AFS voltage output remains the same with engine running after engine is warmed to normal operating temperature. Possible causes are:

• Open or short in AFS circuit.
• AFS.
• ECM.