Hello there! Today I will be hopefully going over some of the reasons a O2 sensor may cause your car to turn off as I just had to work on one myself.

On most vehicles there are at least 2 oxygen sensors the upstream (before the catalytic converter) and the downstream (after the catalytic converter).

Anyway oxygen sensors will eventually need to be replaced on all vehicles it just depends on the year of the car. There is a few signs that I will go over so that we can tell if the car needs a new O2 sensor.

In many cases the first thing noticeable is the decreased fuel economy. A bad O2 sensor will cause the air-fuel mixture ratio to be incorrect. So the car may be running to rich (rich: meaning the engine is receiving too much fuel and too little air.) Which will directly impact the fuel system.

Engine light

Next we have a Blinking check engine light the illuminates or another indicator lamp on your dash. This may be one of the reasons the check engine light is one which in some cases it is.

Another way to tell if there is a bad O2 sensor is a failure to pass the smog test. In the EPA(Environmental Protection Agency) and our happy CARP(California Air Resource Board) 50ish to 60% of all the smog tests and emission test related failure are caused by the defective oxygen sensors. Which may cause really low or really high CO emissions.

Another way is poor performance such as rough idling. Example: when car is running in park and it feels like rumbling and one low RPM from dying.

Stalling is another that is mixed into the rough idling. When the car is running and RPM dips then goes back up to stop the car from dying.

The best way to tell if the vehicle is using a code reader that has a OBD2 checker. Cars from 1996 and up area required to have this interface in their systems.

A code reader with this feature will show you the defects in the cars exhaust system. If the oxygen sensor has failed you. The code will show up if you do a live test or just check through the modules.

Well I hope this helps out it is not much but these are the main causes that an O2 sensor is starting to fail or is failing. Thank you so much for reading this it means a lot!