Contour Enthusiasts Group Archives Forums General General Downstream O2 sensors

I have researched this, and I think I have it right - I am just looking for a confirmation from the knowledgeable people round here.

Downstream O2 sensors are used solely for monitoring the pre-cat efficiency, correct? The upstream sensors help coordinate the MAF with the fuel injectors by telling the PCM if the exhaust gas is rich/lean. The downstream sensors get a value for O2 concentration that the PCM uses to compare to the upstream sensor value and determine if the pre-cat is oxidizing the nasty stuff. Am I semi-correct here?

The reason I am curious is that I have a downstream sensor that is bad. Can I get a set of MIL eliminators (a pair is cheaper than a single O2 sensor) and plug those in and forget about downstream sensors for good? Do you need a functioning O2 sensor for the MIL eliminators to work?

Thanks in advance for you help.