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. DTC is set when AFS output does not change for at least 2 minutes with engine speed at 1500 RPM or more, vehicle speed 25-62 MPH and throttle valve not fully closed. Possible causes are:

• Open or short in AFS circuit.
• Fuel system.
• Fuel injector.
• Ignition system.
• Exhaust leak.
• AFS.
• ECM.