Today, I received my new oxygen sensors (b1s1 and b2s1) from vast performance. I am planning to replace them by myself. Unfortunately, I did not find (via forum search) any sufficient information on how to replace them or location .
I know that these are both front sensors. Probably, I need to remove the cover on the bottom. Then, where should I look for b1s1 and b2s1? Will 22mm/24mm work? Any special tools required?

 

http://www.audiworld.com/tech/eng101.shtml by Shard7

I read the above article and after measuring my sensors discovered that the sensors are perfectly fine. I am still getting CEL codes P1113 (b1s1 - internal resistance too high) and P1131 (b2s1 - internal resistance too high). I learned that getting a CEL code does not mean that one must replace the sensor. The sensor’s job is to identify potential problems. I spent hours under/above the car looking for broken hoses. I cannot see anything bad except that the bottoms of my transmission and oil-pan are a little oily (I guess this is normal for 01 vehicle). Can anybody tell me what should I look for? Again, P1113 and P1131 are still present. I have not replaced them yet since the sensors display acceptable ohms (10 ohms each). Any problem related thoughts are appreciated.

P.S. O2 Sensors for possible sale! I have a pair of sensors (http://vastperformance.com/shop/prod...products_id=69) which I may not need.