My civic speedometer doesn't work occasionally it jumps around to where it should be and then back down to 0. I noticed this happened around the time the o2 busted. I have aftermarket header and it hit something in the road and broke the wire off or something but I noticed it was right after that now it doesn't work right. Could the o2 have anything to do with it? O2 is unplugged and it still does it

 

It sounds like your speed sensor is preparing for the afterlife.

 

It's possible the ss wire runs along the same stretch that got damaged when the oxygen sensor got hit.