Hello Everyone,

I tried running a seach but I can not find anything specific to my car. I have a 2001 A4 1.8T. On another website I found a diy to test your o2 sensor with a multimeter. I located the brown and black connectors on my firewall. The were under the coolent overflow (I think thats what is was). However, my connector had 6 or more pins and on the diy the connector had 4. Are these actually my o2 sensors? I need to replace my post cat sensor and want to make sure I know exactly were it is before I try it.

Thank you in advance.

 

Post means after. The post o2 is the second sensor sticking up out of the exhaust near the firewall. You will see your turbo, primary o2, cat, then post cat o2.

 

So I will need to locate and access this from under the car rather then the top? Sorry for the noob stuff, im just getting started on the DIY...

 

nope from the top. look towards the back of the block and look down and slightly towards the passenger side.

coming off the passenger side of the block is the turbo, behind that is the cat, and the post o2 sensor is the second o2 sensor on the cat. the pre-cat o2 should be real close to the turbo, the post-cat o2 is closer to the exhaust.

here's the best pic i have of it. its with a test pipe and angle block so yours if gona look different, but it should still be in the same location. this is looking straight down at the back of the block