If you notice a drop in your Toyota’s fuel economy, the vehicle runs rough and the exhaust smells strong or the engine is hard to start, you may have a faulty oxygen sensor. The oxygen, or O2, sensor reads the percentage of oxygen in the exhaust coming from the engine and sends this information to the computer. The computer can then determine if the engine is running rich or lean. If an O2 sensor fails, the engine will not run properly.
Locate the O2 sensor connector in the engine compartment of your Toyota. Start the engine and let it run until it rests at a normal operating temperature. While in park, push the accelerator to run the engine above 1200 rpms for two minutes.