Heated Oxygen Sensor



Dear Tom and Ray:

I have a 2000 Saturn LS2 V6 3.0. Recently my Check Engine soon light went on. I took it to dealership and thay diagnosis a P0150 Heated Oxygen Sensor Bank 2 Sensor 1. Where is located? How doew work? Is this serious?


All oxygen sensors are heated. The code indicates that one of your four sensors has failed. This is not a serious problem so you can take your time about repairs. You will need to replace the defective sensor.

Note: It is not necessary to go to the dealership for such problems. Any independent mechanic can deal with this and other issues. They usually charge a lot less money.


If the sensor is actually bad, you may even be able to change the O2 sensor yourself, if it’s easily accessible. Otherwise, pay someone to curse at Saturn’s idiotic O2 sensor placement.


I too have had a service engine soon light come on and stay on and when I take it in the code read bank one sensor 2. I have a 1995 Chevy Blazer. How many sensors do I have? I had one sensor replaced a couple months ago and two years before that. We checked wires and hoses and rehooked that too. Still on. I’m getting frustrated with the car that we can’t figure out what is tripping the light. Any ideas?


If the truck is four cylinder, two sensors. If V-6 or V-8, four sensors. There is one sensor on each exhaust bank before the catalytic converter, used by the computer for fuel management. This is the important one, and is listed as sensor 1. The other is located after the catalytic converter to monitor the converter’s efficiency. This one is for emissions only, and is listed as sensor 2.

Unfortunately, I cannot find my manual to determine which side each bank is on. Hopefully, someone here will know.


Contrary to the advice you recieved, this is the upstream sensor and should be replaced sooner rather than waiting.

This sensor tells the computer how efficient the engine is performing. When it fails, the computer uses a default table of values to determine how much fuel to inject. The result is usually excessive fuel being delivered to default on the “safe” side and if left alone, you could easily kill your catalytic converter over time.