This is my first post to this forum!!

My 2001 A6 4.2 is showing O2 circuit, bank 2 problem code. I have checked Bentley and Alldatadiy.com and it's looking like I'll have to change the sensor. Mileage is 104000.

Some questions-
1. Manuals say remove front exhaust pipe with cat to get to O2 sensor. This sounds like a big job, but Alldatadiy gives the flat rate at 0.9 hours (warranty) or 1.4 hours (customer expense). Is it really that straightforward to take these pipes off? Or can I get to it from the topby moving the coolant recovery jug aside? One photo in the manual shows this, but it may be a V6.

2. It's possible it's a wiring or power problem. Is there a fuse somewhere for the O2 heater circuit? I don't see one anywhere in the wiring diagram.

Just finished the outboard CV joint replacements (both outboard boots went at about 99000 miles within 2 weeks of each other), and all new front brakes. Getting ready to do the timing belt next, but the O2 sensor problem cropped up and it's due for inspection sticker in May. I may hold off on the timing belt until after I clear inspection.....

Thanks for any insights you can give me on the O2 sensor questions.
Jim

 

First of all welcome! I have the same problem with the 02 sensor. My 01' A6 2.7t is running codes P1136 and P1138. Have you checked all the hoses and vacs? Make sure you do that before you do anything major such as removing exhaust pipes. I will be checking over mine today. Make sure everything is connected correctly and snugly. Also, the timing belt is a big problem and with the milage you have on it, it is something that shouldn't be ignored. If it breaks it could do major damage to your engine, head gaskets etc... I have 83k on mine and will be getting it checked out soon. Good Luck!

 

FYI

A failed TB does not hurt the head gasket unless you conside having to take the motor apart to replace valves pistons etc hurting the head gasket. Audi has an interference motor. That means that the valves and pistons occupy the same space in the combustion chamber but at different times. When the timing belt breaks the valves and pistons get confused and attempt to occucy the same space AT THE SAME TIME. This usually resultsin bent valves but the valves can also poke a hole in the piston or it might break a cam bearing or cam. In any case it means spend $$$$ What do they say --Pay me now or pay me later!

 

My bad. Thanks for correcting me.

 

Thanks for the tips. I'm using a "CarChip" for the codes. I'm getting a PO150. Oxygen sensor circuit malfunction, Bank 2 Sensor 1.

It's my fourtherror code over the last 3-4 years. First time wassecondary air injection system, fixed with new vacuum hoses to the secondary air injection valves- factory hoses were junk. Second time (PO171 and PO174 system too lean) was fixed for 6 months by cleaning the MAF sensor, then finally by replacing it.

So last weekend I unscrewed the coolant recovery reservoir and set it aside on its hoses. I could peer down between the head and the firewall and actually see the O2 sensor. I'm 80% sure I can actually reach down and touch it (engine was hot and I wasn't dressed for the job so I didn't try), and I think I can get on it with a crows foot O2 sensor socket. I also saw that the exhaust pipe (nice shiny stainless steel) connects to the manifold on studs, and not with bolts as I had been told, soI'm REALLY leary of trying to pull the exhaust pipe my self anyway, afraid of breaking studs. I'll take another look this weekend on a cold engine, then pick up a sensor socket and have at it. I'll take a picture of my approach if I can pull it off.

I'm beginning to think that the repair manuals are at least partly based on factory assembly procedures. And in the factory the sensor is installed in the manifold first and then into the car. Once in the car, I'm convincing myself that I can swap it without backtracking through the assembly order. It'd belike pulling the head first to replace the spark plugs....

Jim

 

Well, it worked. By moving the coolant recovery bottle to the side- didn't need to disconnect it or empty it- I could reach down and grab the O2 sensor with my right hand.

First I disconnected the sensor wire from the harness at the bulkhead connector attached to the firewall. Then, I put the crow's foot socket onto the sensor with my right hand, and then snaked a long3/8" extension down from the left near the center of the V of the engine. I tried various arrangements of 3/8 extensions and flex joints, but ended up using just a straight long (18" maybe) extension. Play around with the orientation of the socket on the sensor until you find a position to engage the extension coming in from the left. A wobble extension on the end where it mates to the socket may have helped. Having thefoot of the socket point roughly foward on the car worked for me.

Once set up, the sensorpopped with little hassle, and then unscrewed by hand. Reassembly was fast. Icarefully guided the new sensor into position down from the right andcould hand tighten it. Wasn't sure of the torque, so I tightened it to 22 ft pounds- same as a spark plug.

Turned out the longest part of the job was splicing the new Bosch universal sensor to the old connector, using the splice andthe instructions that came with the sensor.

Piece of cake. Sorry, no pictures.... I forgot until I had it all buttoned up.

Next-still have to see if the error code will go away! Then on to the dreaded timing belt job.

Jim

 

Jim,

did theerror code go away, after you replaced the oxygen sensor??

 

Worked! No codes since 3/22. Passed inspection on May 3, and so now I'm in the middle of the timing belt. What a job this is!

 

I to have oxy sens. codes.( on my 4.2 )the Ebahn site says to check fuses but I CANNOT find them!!!!!
I can find NO info on where they are? Does anyone know??
BENG

 

I looked as well, to no avail. What codes do you have?