What should O2 sensors read at idle?
The voltage generated from the O2 sensor should be from 0.1V to 0.9V, with 0.9V on the rich side and 0.1V on the lean side. If your readings are within this range, the O2 sensor is functioning properly.
A properly functioning oxygen sensor will show a rapidly fluctuating output voltage between approximately 0.1 and 1.0 volts. The time taken for the voltage to change from 0.1 V to 1.0 V (referred to as the lean to rich response time) should be about 300 milliseconds.
- Make sure the engine exhaust system is cold.
- Switch the clamp-meter on, to 'DC current/DC amperage' mode.
- Put the clamp around either of the oxygen sensor heater power wires (but not both). ...
- Turn the engine on.
- Observe the reading, which should be between 0.25A and 1.5A.
It should be fixed for a short period at around 0.1 or 0.2 volts. 2) After two or three minutes, the voltage reading will begin to fluctuate between 0.1 and 0.9 volts. If the sensor takes four minutes or more to begin fluctuating, replace it.
So how can you check if the catalyst no longer can store 02, look at the rear O2 sensor? If the catalyst is working the rear O2 should be flat or steady. If the O2 sensor in the rear is switching with 70% of the front, this may indicate a bad catalyst or a cat that's not efficient.
Long-term fuel trim values
Ideally, long-term fuel trims should be at, or close to 0% when the engine is running at a steady speed. However, while changes to the engine speed will (and must) produce changes in the long-term fuel trim value, this value should return to a point close to 0% when the engine speed steadies.
- Insert the OBD2 scan tool connector to the diagnostic link connector (DLC) on your vehicle. ...
- Turn on your vehicle's engine so that the scanner can communicate with the vehicle's onboard system. ...
- After the scanner boots, go to the menu and select 'Trouble Codes' or 'Codes'.
With the ignition on, the MAP sensor output should be around 5 volts. Start the engine and check the reading; at idle, the MAP sensor should read 1 to 2 volts. This indicates the MAP sensor is responding to changes in vacuum.
Stop and idle for 30 seconds. Then smoothly accelerate to 30 to 40 mph. Repeat the last two steps five times. Toyota: The oxygen sensor monitor should run after idling the engine for nine minutes, then driving at a steady 25 mph for two minutes.
Once the converter lights off, the downstream O2 sensor will settle down and “flat-line” at a steady voltage reading usually around 0.45 volts or so.
How do I know if my O2 sensor is good?
Don't Buy Oxygen Sensors! How to test o2 sensor - YouTube
They both function the same but are different enough that they cannot be swapped.
The real problem may not be a bad O2 sensor, but possibly be an engine vacuum leak, low fuel pressure or dirty fuel injectors that are causing the engine run lean. An engine misfire, leaky exhaust valve or a leak in the exhaust manifold gasket that allows air into the exhaust may also cause this type of code to be set.
A low voltage signal from the oxygen sensor indicates low oxygen content in the exhaust—a sign that the engine runs rich. The PCM responds by reducing the fuel going to the engine.
Understanding & Live Graphing of the Rear O2 Sensor - YouTube
The basics on live data obd2 scanner - YouTube
The high voltage condition from the O2 sensor is indicating a lack of oxygen in the exhaust or other related problems, such as a leaking fuel injector or a broken up catalyst inside.