Diagnostic Aids
WARNING: This page is about a different car, the 2003 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0134 or P0154 set when A/F sensor output does not change when the following conditions are present for at least 1.5 minutes: A/F sensor output does not set when engine speed is 1500 RPM or more, vehicle speed is 25-81 MPH, and throttle valve does not fully close. Problem areas include fuel system, injector, ignition system, gas leakage on exhaust system, open or short in A/F sensor circuit (bank 1, 2 sensor 1), A/F sensors (bank 1, 2 sensor 1), PCV valve and hose, or ECM.