Circuit Description

WARNING: This page is about a different car, the 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.

Air/Fuel (A/F) sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. ECM uses input signal to control air/fuel ratio. A/F sensor includes a heater. DTC is set when A/F sensor output does not change after 140 seconds from time engine is started, 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 A/F sensor circuit.
Faulty A/F sensor (bank No. 1 or 2, sensor No. 1).
Faulty air induction system.
Fuel pressure malfunction.
Faulty fuel injector.
Leaking exhaust system.
Faulty ECM.
PCM piping.