spoon2000

Can anyone please give advice on replacing the bank 1 side 1 O2 sensor (passenger's side, between engine and cat)? I can't figure out the best way to get at it with the tools, and Bentley is not much help. Do the exhaust or the RF wheel have to come off? Is it best to get at it from the top or from underneath? This is for a 2001 C5 4.2.

Many thanks.

pearlwhitesix

I would love to know as well, I need to replace mine. I was able to replace the drivers side fairly easily. When I attempted mine there were too many things like coolant pipes in the way to get a good look at it.

SloopJohnB@mac.com

Several long extensions, flex joint, from bottom according to STFA.
Hint: cut the cable off the sensor at the sensor and you can use a deep socket.

You'll have to use and 02 sensor wrench to put the new one in with the cable.

Some people like to use a universal Bosch sensor and reattach the old cable (I like solder electrical joints BTW) but make sure you get the new design/rapid response sensor.

Redneck Truck

I did this job several months ago. I believe I finally reached it from the top with a plain old adjustable wrench and a TON of patience. Even though my car is a northern car, after the initial "pop" that broke the sensor loose, it threaded out and the new one threaded in by hand.

That said, my SAI has been deleted, so that might have made the job easier for me.

rocketman4321

I got it from the top, used an offset (crow's foot-type) sensor socket and a variety of long extensions and u-joints. Tape the tools together so you don't detach a long extension and the socket in a deep dark place.

The disconnecting/prep was either per Bentley or one of the posts here.

spoon2000

OK, I did the bank 1, side 1 (i.e. passenger side, pre-cat) oxygen sensor replacement yesterday. WHAT a miserable job. In a nutshell for others who may follow on an A6 with the 4.2 engine:

1) Remove all the air intake tubing between the air filter box and the back of the engine. Also remove the black plastic top decorative cover on the engine.
2) Locate the wire running to the O2 sensor, disconnect it at the wiring harness, and separate it from the other wires nearby.
3) Kneel on top of the metal intake manifold (use a soft pad or something to protect the engine and your knees). Re-route the O2 sensor wire so that it follows as path that's as vertical as possible between the top of the O2 sensor and the top of the engine compartment. Slide the O2 sensor socket over the wire and then tape around the socket with electrical tape so that it can't slip off the wire.
4) Slide the socket down the wire until it bottoms-out on the O2 sensor.
5) Reach down with your hand (may be difficult if you have a large forearm) around the back of the engine and arrange the O2 socket such that you can see the hole where the ratchet (or in this case ratchet extensions) attach to the socket. Use a shop light to help you see what's going on.
6) Assemble a socket wrench consist as follows: universal joint on the bottom, and then two 10" extensions (or the equivalent) above it. Use electrical tape to hold the universal joint and the extensions together so they don't come apart.
7) Insert the socket extension consist down from the center rear of the engine toward the O2 sensor at roughly a 45 degree angle. Reach down with your hand to guide the bottom of the universal joint into the hole on the O2 sensor socket.
8) Insert a breaker bar or similar leverage tool into the top of the socket extension consist and turn. In my case the O2 sensor loosened immediately.
9) Disconnect the extension consist and set it aside.
10) Reach down with your arm and unscrew the sensor by hand, or else use the O2 socket to help unscrew the socket. Keep untwisting the O2 sensor cable as you go or else the socket will be harder to unscrew.
11) Untape the O2 sensor socket and remove from the old O2 sensor wire, and then re-attach it onto the new O2 sensor wire as before with electrical tape. Install the new O2 sensor, tighten by hand, and then attach the extension consist into the socket and tighten.
12) Plug the new sensor into the wiring harness, re-assemble the air intake tubing, and put the cover back on the engine. If necessary, get a blood transfusion to make up for what you've lost from cuts and scrapes in your hands and forearms.

A couple other notes:

1) I used the generic Bosch O2 sensor (Bosch part number 15733 -- best prices seem to be at Amazon.com) rather than the the one with Audi-specific connector already attached to it. It takes about 15 minutes to splice the connector from the old sensor onto the new sensor's wiring, and it's an easy job (the instructions are very clear and all the parts are included). The generic O2 sensor is substantially cheaper than the one that comes with the Audi-specific wiring harness connector already attached.
2) There is a small plastic tube that starts at the coolant expansion tank, runs along the firewall, turns toward the front of the car and goes under the air intake tubing, and terminates at the radiator hose. If you break this tube as I did multiple times in multiple places (it seemed quite brittle), don't worry -- just go to the hardware store, get some rubber tubing (5/16" inside diameter fuel line hose worked for me) and a couple of aircraft clamps, and splice in the tubing to replace the broken section of plastic pipe. It works great, and I have used this solution elsewhere in the engine compartment to avoid having to pay Audi dealer prices for the OEM hose/tubing part (in particular, I used dishwasher drain hose to replace some tubing down in the lower right front corner of the engine compartment that feeds the secondary air pump).

Cheers and good luck.

Airbag

i have to do the bank one sensor 2 sensor now as the check engine light is on very often and we have new laws for emmisions now.

anyone know the part number or availability of a generic for that location ? spoon gave me a part number a while ago but i dont know if that was fro front or rear.

180 bucks is the cheapest i have seen for the rear and that is about 10% the worth of my car !!!

thanks for any info

spoon2000

The Bosch 15733 O2 sensor is "universal" and will fit in any of the 4 locations. It's $46 with free shipping at Amazon. You'll have to splice the wires but it's an easy task (all needed parts are included) and if you want to save the money, it's the way to go. Here is the link:

Airbag

thanks spoon

i picked up a couple today in niagara falls at an online place and went and pikcked up worked out to 45 each and i didn't have to wait.
i'll let you know bow it goes

Backfixer3011

Maybe this can help