Circuit Description

WARNING: This page is about a different car, the 2002 Toyota Tundra. However, it is still accessible from the selected car via links, so may be relevant.

Heated oxygen sensors located on each exhaust manifold monitor exhaust gas oxygen content and deliver input signals to ECM. Heated oxygen sensor on driver's side exhaust manifold may be referred to as bank No. 1 sensor No. 1 and heated oxygen sensor on passenger's side exhaust manifold may be referred to as bank No. 2 sensor No. 1. ECM uses input signal to determine fuel injection system operation. DTC is set when heated oxygen sensor bank No. 1 sensor No. 1 or heated oxygen sensor bank No. 2 sensor No. 1 does not output a rich condition (output voltage equal to or more than .45 volt) even once after engine is started with engine at normal operating temperature, engine speed of 1400 RPM or more and with vehicle speed of 25-62 MPH for at least 1.5 minutes. Possible causes are:

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