I have a 2002 a4 3.0 w/ dual exhaust and I need to replace oxygen sensor # 2 in bank one what is the location of this sensor , i know its on the passenger side. someone told me i have to takeout the air box and the boot to get at it.

Isn't #2 the postcat sensor? That one is accessible from underneath the car. If the 3.0 is anything like the 2.8 its a pita to get to the precat sensors.

Yeah, #2 is post-cat. And yeah, pre-cat sensors on the V6 are a major PITA.[:@]

do u know the location of the post cat sensor ? when i get under the car the only one i can see is the sensor before the cat

The 3.0L O2 sensors are almost right next to each other. The post cat O2 sensor is the one you CAN see in the middle of the cat converter. The Pre-cat O2 sensor you can't see which is almost bolted right at the back of the cylinder head, if you reach around behind the head you can feel it.
On the 3.0L engine, none of the O2 sensors are under the car.

when i lay under the car i can see an 02 sensor,itlooks like its right in front of the cat, is that the post cat?

Goodluck replacing it, everything is hard to do on the b6 3.0, specially oxygen sensors, u cant even fit a tool to get them off.

Similar Qs:for O2 locations on a 3.0

I have a code (P0431)for Bank 2 Warm up Catalyist;
1) Which one is theWarm up (heated?) sensor? Post or Pre Cat?
2) What about theBank designations, Bank 1 and 2, Which one is which? Driver or passenger side?

6-Cylinder Engines:

Bank 1 (Passenger Side)
Pre-cat sensor (B1 S1)
Post-cat sensor (B1 S2)

Bank 2 (Driver Side)
Pre-cat sensor (B2 S1)
Post-cat sensor (B2 S2)

I found this, and all sensors are the heated type

goto: http://www.audiworld.com/tech/eng.html

If you just have code > P0431 and no other O2 codes.

it does not necessarily mean your O2 is out.
often it is the cats itself out.


I got two codes > First P0431, after 2 monthes, P0421.
Dealer checked all 4 O2 sensors' voltage and working fine.
Turned out to be cats.
replacing both cats under federal emission control warranty with dealer.


It is common known problem that 02 AVK-3.0's cats fail at early milage. (from 70k)

Check:
http://autos.msn.com/research/vip/Reliability.aspx?year=2002&make=Audi&model=A4&trim id=-1

Thanks for the link, I had my oil pick tube repaired 2yrs ago (under warranty).There some validity to common problems.

If thisis my 1st cat failure..... sounds expensive to what i've justread on the link. Whats the "federal emission control warranty with dealer". Is there a federal rule that dealer must comply too above manufacturers warranty (which is expired).

I goggled federal emission control warranty, yep a warranty for8yrs 80kmiles. I spoke to the dealer, they made it sound simple. They need to verify the code... Set Readnesson the computer, and wait for the code (MIL) to return. I once had resetted the code and it took 4 wks to return. Dealer wants 1hr labor to "set readiness" = $109.00.

same thing to me.

They've ordered both cats from germany.

going to take 4-6 weeks of delivery.