Circuit Description

Heated Air/Fuel (A/F) sensor monitors exhaust gas oxygen content and delivers input signals to ECM. Heated A/F sensor is located on exhaust pipe in front of catalytic converter. A/F sensor may also be referred to as A/F sensor (bank No. 1 sensor No. 1) or A/F ratio sensor. ECM uses input signals to determine fuel injection system operation. DTC is set when A/F sensor output voltage does not change after engine is started with engine at normal operating temperature, engine speed of 1500 RPM or more and with vehicle speed of 25-62 MPH for at least 1.5 minutes. Possible causes are:

• Defective Positive Crankcase Ventilation (PCV) valve hose or connection.
• A/F sensor circuit is open or shorted.
• Defective A/F sensor.
• Air induction system malfunction.
• Improper fuel pressure.
• Defective fuel injector.
• Exhaust system leak.
• Vehicle has run out of fuel.
• Defective ECM.