I'm going to be changing my precat oxygen sensor. Would it be a waste of my time to disconnect the battery to reset anything? Or just replace the sensor and drive on?
Thanks

 

You should always reset your PCM when you change an engine sensor or any component that effects engine operation.
If you are changing the sensor for maintenance it's not as important but if you have a actual problem or fault its a verygood idea.

 

so how do you reset the pcm

 

If you don't have a scan tool disconnect battery and turn ignition on.5 minsshould do it.
This will erase the PCM adaptive memory.
Be advised that it can take 500 miles for the PCM to fully relearn and adapt to your engine.
You might experience a rough idle and reduced economy for a while.