How to Test the Toyota Oxygen Sensorby Christian Killian
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.
Unplug the connector from the O2 sensor and place the positive lead from a digital multi meter on it, then attach the negative lead to the battery. Set the meter to 12VDC and watch the display.
Note the readings on the meter. The voltage should fluctuate between .40 and .60 volts rapidly. If it does not, replace the O2 sensor. If the voltage is within the specified range but does not fluctuate or does so slowly, the sensor should be replaced.
Remove the meter and plug the connector into the wiring harness. If your Toyota has more than one sensor, repeat the test on each sensor to determine if any are faulty. Shut off the engine when you are finished testing.