Originally Posted by snrusnak
They vary by vehicle, I've seen them as cheap as $20 and as expensive as $150. Most fall in the middle somewhere.
Why do you want to replace them? The 2 downstream sensors are likely a different part number than the upstream sensors, also. The 2 upstream sensors are the only ones that would cause a real running issue.
Not to knock mechanics, but many of them don't understand how the system works. Often times it can even not be a faulty O2 sensor but something else making the sensor through a code.
You have a check engine light? What's the code?
I have a code "0300" which is "random misfire" which tells me nothing. The truck runs good but every once in awhile it will drop a couple of cylinders, the check engine light starts flashing and it sets the code. You drive it and it will suddenly fix itself. So, I heard that a bad O2 sensor can do this so maybe I'll just change the 2 upstream ones.
Thanks for the info.