O2 Sensor

[I Audi5K I]

How hard is it to replace? Any DIY's? Recommended places to purchase? Thanks!

[jursch2211]

I would order one from ECS or genuineaudiparts.com. I think the ECS one is actually cheaper. Not hard to do at all if its the front O2 sensor. The rear one will be a little bit more difficult. I just did my front one and it took me about 20 minutes. Just unplug and unscrew the sensor from the catalytic converter and replace in same order. Check A4mods.com. I just did my front and I'm debating whether to do the rear as well. Anyone know if it's necessary?