I have a 99 civic dx that has a check engine light on and when auto zone coded it for me they said it was o2 sensor number 1. Well there are 2 of the little boogers on this car and neither are cheap. is there any way to know which one is which so that i don't have to change them both? I am trading the car in sometime in august so i don't want to lose a ton of money on this.

 

I'm guessing the first one would be the one that's on the exhaust manifold (the one that's easier to access. And the second one would be the one closer to the cat. converter.