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DIY/HOW-TO: C5 A6/B5 S4 2.7T OXYGEN (O2) SENSOR REPLACEMENT W/ PICS- MUCH REQUESTED!!

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Old 02-03-2010, 04:57 PM   #1
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Default DIY/HOW-TO: C5 A6/B5 S4 2.7T OXYGEN (O2) SENSOR REPLACEMENT - MANY'VE REQUESTED!!

D.I.Y/How-To: Oxygen (O2) Sensor Replacement on Audi (C5) A6 2.7T / (B5) S4 2.7T

It is finally here! After hours of searching the forums myself for a good tutorial on how to change the Pre/Post cat O2 Sensors on a 2.7T - I was never able to come across anything but hundreds of people pleading for one - with descriptions, pictures, details, etc. Well folks, HERE YOU GO! I must say, I am happy to be the one to provide you with this information, however and like always, this must be said:

DISCLAIMER:

I, Ben C. (aka 01A6Turbo), hold no responsibility, should you (the reader of this tutorial) choose to attempt this repair work amongst yourself, without seeking the help of a professional. I hold no legal liability/responsibility should something within the event of you following my instructions cause damage or injury to yourself, your vehicle, or any other matter. I am posting this how-to tutorial as a follow guide due to a lack of available information/photographs/et. all for the Oxygen (O2) Sensor Replacement repair on the Audi (C5) A6 2.7T and Audi (B5) S4 2.7T engine models.

THE HOW-TO:

Okay, so your fuel economy has sort have been down in the dumps lately; possibly your reaching that "100k" mark Bosch claims their sensors last up to and it's time to check them; or maybe your car isn't idling/running as smooth as she was the day you purchased her; perhaps your CEL (Check Engine Light) has illuminated and you ran to your local auto store and the guy behind the counter told you one or more of your Oxygen Sensors were throwing codes and needed replaced. Well, that's why we're here! So let us start with the #1 most important thing of the day….

Click the image to open in full size.
MmmMmmmMmmm Have to love that Jo'!

OVERALL DIFFICULTY:
===================
On a scale 1 - 10 (10 being Audi Certification Required), I give this job a true 6 or 7.

ESTIMATED TIME OF JOB:
=====================
Approximately 3-6 hours depending on mechanical skill level, age of old sensors, ability to move about like a gymnast It personally took me 4-4.5 hours and this was my first time doing O2 Sensors.

VEHICLE PERFORMED ON IN TUTORIAL:
================================
2001 (Build Date 05/00) (C5) Audi A6 2.7L Twin-Turbo V6 30v

TOOLS NEEDED: (More or less depending on your mechanical skill level - these are the tools I personally used)
==============

Replacement Oxygen Sensors (See photo below for part #s)
1 22mm O2 Sensor Wrench AND/OR 1 22mm Crow's Foot (solely based on preference/availability of the tool)
1 Phillips
1 Flat head screw driver
1 Can PB Blaster (or similar)
1 1/2" Ratchett
2 1/2" one (1) foot extensions (total of 2 feet)
1 Universal Socket
1 10mm Socket
1 pair of large needle nose pliers or similar (to remove MAF to Y-Pipe Accordian hose clamp)
Anti-seize
4-6 Zip Ties
Flashlight
1 Roll of very strong tape (I used USPS Shipping Tape)
1 VAG-Com AND/OR OBD II Scan Tool (if reason for this repair is CEL/Codes)
1 Pair Snips/Scissors


*** BE SURE TO DO THIS WITH A COMPLETELY COLD ENGINE ***


Click the image to open in full size.
Here are some, not ALL of the tools I used. I had to add tools as I went further into the job not really knowing exactly what I'd need. However these are the essentials to start out with!

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Step 1: Remove the engine cover pieces outlined in YELLOW by hand. They simply lift up and off.
Step 2: With a Phillips screwdriver - Unscrew the pop-up plastic screws and remove the engine covers.
Step 3: Remove 3 metal screws on the coolant reservoir tank with a Phillips.
*** Step 2 & 3 Outlined in RED ***

Step 4: Once coolant reservoir is unscrewed, carefully lift tank off of metal holding plate and located the sensor wire connected to the bottom. With a flathead screwdriver, being careful not to break the clip, disconnect this sensor and move the coolant reservoir out of the way. (Side note: At this time, I also removed the black engine cover on the side of the valve cover/side of manifold. Be sure to remove the oil cap before lifting up on this cover (after unscrewing 2 pop-up plastic screws just as in Step 2 above. Replace the oil cap once cover is removed.)

*** OFF TO THE PASSENGER SIDE NOW ***


Click the image to open in full size.

Step 1: Remove/unclip the four (4) connectors to your two (2) ICMs (Ignition Control Modules). (Circled in Yellow) Simply push down on metal clip and slide off connector.
Step 2: Unclip two (2) clamps connected onto your fuel lines (Circled in Cyan/Baby Blue)
Step 3: Remove MAF housing from Airbox (Circled in Dark Blue) - there are two of these clips directly Left & Right from each other. Don't lose the O-Ring inside!
Step 4: Unclamp the Airbox's clamps (4) that connect the Top & Bottom of the Airbox together (Circled in Lime Green). The 4th is on the MAF housing corning, down below. Hard to reach.
Step 5: Now with your large pliers (or similar tool), remove the accordion hose from the silver Y-pipe. Squeeze the clamp together and it will open up, allowing you to slide off the hose.

Next to the accordion hose, this is where you will now see three (3) of your four (4) connector harnesses with connectors for the Oxygen Sensors.
Click the image to open in full size.

*** REMOVING Y-PIPE ***

If you are like me and do not have any spare 1-time clamps lying around, I came up with another method to remove the Y-Pipe and never have to worry about tampering with those clamps.
Click the image to open in full size.

Step 1: Remove three (3) 10mm bolts located near the rear of the Y-Pipe, near where you just removed the accordion hose. Next, follow the Y-Pipe down to where it splits and heads down the side of the manifold. Next to your Coil packs 1 & 4 (near the front of the engine) you will see two more 10mm bolts. Remove these. All necessary bolts to be removed are circled in RED in the above photo.
Step 2: Head back to the rear of the Y-Pipe and you will see part of the Spyder hose assembly connected to a little off branch next to the curve in the pipe. It is black and plastic. Squeeze down on the top and bottom of this and pull it off.
Step 3: If you have already replaced your DVs (Diverter Valves), you probably already have reusable hose-clamps installed. Using a flat head screw driver, loosen these hose-clamps and remove the black tubing from the Y-Pipe, from the DV. (Circled in GREEN in the above photo).

Your Y-Pipe should now be free to be removed. Your engine should now look like my photo below.
IMPORTANT: TO ENSURE NO DIRT/DEBRI/ETC GETS INTO ANY UNWANTED PLACES, USE CLEAN SHOP RAGS AND COVER OF HOLES OF THE PIPING YOU JUST EXPOSED FROM REMOVING THE Y-PIPE!!

Click the image to open in full size.


Now that you have everything needed to be removed out of the way (Coolant reservoir, Air box, MAF housing, Accordion hose, Y-Pipe), using your flashlight you should be able to see the passenger and driver side O2 sensors. First we will go over the passenger side as it is easier to remove then the driver side.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Remove the Passenger Side Pre-Cat Connector from its retaining harness by sliding it forward and out. Once removed from the harness, depress the two clips and slide the two connectors apart shown below:
Click the image to open in full size.

Spray and SOAK that baby with PB blaster. The angle is a little hard, but after a few short, gentle sprays, you'll be able to determine exactly how to spray it where the sensor meets the bung of the CAT. Allow it to soak for 10-15 minutes if your sensors are older (mine had 115k miles on them. They weren't going anywhere!) You may want to repeat this step a few times depending on age.
Click the image to open in full size.
Click the image to open in full size.

Now with your rig'd tool (O2 wrench, Universal, 2 foot extension, ratchet) that is securely taped/tied together (you do NOT want to drop anything down below and at this angle, it is very easy to lose your O2 wrench/crow's foot! Better to be safe than sorry!)) slide it over the O2 sensor wire and down onto the sensor. If you aren't able to loosen the sensor with some elbow grease/muscle, try the old mechanic's method of tightening first, then loosening. Or you may try what I did and get a rubber hammer and pound away at the ratchet knocking her loose. It is easier said than done, be warned! To get off my passenger pre-cat, I probably fought with it for a good hour or so!! Once she comes loose, reach down and hand loosen her off. Your retaining clips should already be cut - just pull the sensor up and out.

Apply anti-seize to the threads of the new sensor, reach down and hand tighten her. Be careful not to twist the wires of the new sensor while doing so! I used my left hand to turn the wires as I tightened the sensor with my right hand. Get your rig tool again and give her a good nice tighten - doesn't have to be extremely tight, you don't want to fight her as much next time as you did this time if she needs to be replaced again! Re-thread the wire the way you feel is best, applying zip ties along the way. Try to stick to the OEM setup for best results. Attach the new connector-sensor end with the connector-ECU end, reinsert both connectors into their appropriate harness and congratulations, you are now done with the passenger side!

Now onto the PITA driver side. We do not lie about this…this sensor, due to it's angle and limited availability on the 2.7L engine puts the ITCH in BITCH. ROTFL.

Click the image to open in full size.

Click the image to open in full size.

Sorry the picture is out of place but this (circled in YELLOW and RED) are the pieces of the Spyder assembly I was referring to above that were disconnected.

Click the image to open in full size.

The hardest part of removing the driver side O2 Sensor is it's angle. If it wasn't for that, it wouldn't be so bad. However, I, as well as many others, agree it is best to approach it from the passenger side of the engine bay, using your 2 foot extension, universal socket and O2 wrench/crow's foot. This sensor honestly took me a good 2-2.5 hours to get off! It got drenched in PB blaster for 20 minutes at a time, for about 5 times! I honestly kicked, cussed, cursed and threw a tantrum trying to get that sucker out. Do some breathing exercises to calm yourself before attempting this one! loll

This side is done the same as the passenger although below the connector you have a heat shield with two buttons that needs released, and 2 retaining clips that need cut. Once loosened with the wrench/crow's, again, hand loosen the rest, and carefully pull the old sensor out. Anti-seize the threads on the new sensor, hand tighten her down, then grab your wrench/crow's, like the passenger, tighten her down, rethread your wires, applying zip ties in factory location or some where close to, connect the sensor connector with the ECU connector, reinsert into the harness housing and give yourself a great big pat on the back! The two hardest sensors are complete.

Click the image to open in full size.

As most here say - reinstall everything in the reverse order. Again, congratulations on a job well done!!!

Last thing's, last. If your old O2's were throwing a code, hook up your VAG-Com/OBD II Scan Tool, erase the code(s) and remember to take her on a drive cycle so the ECU can relearn all of it's 9 categories with the new sensors! Even if you weren't throwing codes, this is still a good step to complete.


Now, even though I have not done my post-cat's (I ordered them at the same time to have them as back-up, plus got a wonderful deal on them from amazon.com - but I will worry about doing these when the weather is a bit more kind.) the process is the exact same - only EASIER!! I bet that put a smile on your face. The only difference being these are located after the cat-converter and must be attained from underneath the vehicle. If you are doing these at the same time as your PRE's, just add a jack lift and two jack stands to your list of tools needed. PLEASE if you are unfamiliar with the proper way of lifting a car, refer to your OEM Manual AND/OR the Bentley Publisher's manual. Always secure ANY vehicle with the parking brake applied, blocks in front of/behind of the rear tires and ensure that the vehicle is safe and sturdy before EVER climbing underneath one.

I truly and honestly hope this HOW-TO Tutorial has and will help many of you in the future. I have just spent the last 2.5 hours preparing the pictures, and writing this tutorial - I thank all of you that has ever helped me in the past and am always happy to provide back to our little community of Audi Worlders

Good Luck & God Bless!


- Ben - (01A6Turbo)
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Last edited by 01A6Turbo; 02-03-2010 at 06:04 PM.
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Old 02-03-2010, 06:33 PM   #2
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Awesome! thank you so much this will come in handy
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Old 02-03-2010, 09:10 PM   #3
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BTDT! And the driver's side is a total PITA! The key for the driver's side is removing/unplugging everything you described especially the heat shield. o2 sensors, a bitch but it can be done.
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Old 02-04-2010, 12:53 PM   #4
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Quote:
Originally Posted by makav3li View Post
Awesome! thank you so much this will come in handy
You're welcome

A62.7T4ceo: Yea tell me about it...PITA can't even describe the sucker lol
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Old 02-04-2010, 08:43 PM   #5
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Drivers o2 is an amazing PITA! I wonder how the ecs tool would work?

http://www.ecstuning.com/Audi-C5_A6-...ical/ES240942/
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Old 02-04-2010, 11:08 PM   #6
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hmm probably a little better than my taped together contraption lmao - however mine was free...$30 for that!? Definitely overpriced...
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Old 02-05-2010, 12:03 PM   #7
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Quote:
Originally Posted by 01A6Turbo View Post
hmm probably a little better than my taped together contraption lmao - however mine was free...$30 for that!? Definitely overpriced...
Haha! Same for me...Taped like 6 socket pieces together(Oh and a magnet on a stick for when a piece falls off!). I would pay $30 for it, if it worked.
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Old 03-27-2010, 11:53 AM   #8
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Default how to check 02 sensor

Quote:
Originally Posted by 01A6Turbo View Post
D.I.Y/How-To: Oxygen (O2) Sensor Replacement on Audi (C5) A6 2.7T / (B5) S4 2.7T

It is finally here! After hours of searching the forums myself for a good tutorial on how to change the Pre/Post cat O2 Sensors on a 2.7T - I was never able to come across anything but hundreds of people pleading for one - with descriptions, pictures, details, etc. Well folks, HERE YOU GO! I must say, I am happy to be the one to provide you with this information, however and like always, this must be said:

DISCLAIMER:

I, Ben C. (aka 01A6Turbo), hold no responsibility, should you (the reader of this tutorial) choose to attempt this repair work amongst yourself, without seeking the help of a professional. I hold no legal liability/responsibility should something within the event of you following my instructions cause damage or injury to yourself, your vehicle, or any other matter. I am posting this how-to tutorial as a follow guide due to a lack of available information/photographs/et. all for the Oxygen (O2) Sensor Replacement repair on the Audi (C5) A6 2.7T and Audi (B5) S4 2.7T engine models.

THE HOW-TO:

Okay, so your fuel economy has sort have been down in the dumps lately; possibly your reaching that "100k" mark Bosch claims their sensors last up to and it's time to check them; or maybe your car isn't idling/running as smooth as she was the day you purchased her; perhaps your CEL (Check Engine Light) has illuminated and you ran to your local auto store and the guy behind the counter told you one or more of your Oxygen Sensors were throwing codes and needed replaced. Well, that's why we're here! So let us start with the #1 most important thing of the day….

Click the image to open in full size.
MmmMmmmMmmm Have to love that Jo'!

OVERALL DIFFICULTY:
===================
On a scale 1 - 10 (10 being Audi Certification Required), I give this job a true 6 or 7.

ESTIMATED TIME OF JOB:
=====================
Approximately 3-6 hours depending on mechanical skill level, age of old sensors, ability to move about like a gymnast It personally took me 4-4.5 hours and this was my first time doing O2 Sensors.

VEHICLE PERFORMED ON IN TUTORIAL:
================================
2001 (Build Date 05/00) (C5) Audi A6 2.7L Twin-Turbo V6 30v

TOOLS NEEDED: (More or less depending on your mechanical skill level - these are the tools I personally used)
==============

Replacement Oxygen Sensors (See photo below for part #s)
1 22mm O2 Sensor Wrench AND/OR 1 22mm Crow's Foot (solely based on preference/availability of the tool)
1 Phillips
1 Flat head screw driver
1 Can PB Blaster (or similar)
1 1/2" Ratchett
2 1/2" one (1) foot extensions (total of 2 feet)
1 Universal Socket
1 10mm Socket
1 pair of large needle nose pliers or similar (to remove MAF to Y-Pipe Accordian hose clamp)
Anti-seize
4-6 Zip Ties
Flashlight
1 Roll of very strong tape (I used USPS Shipping Tape)
1 VAG-Com AND/OR OBD II Scan Tool (if reason for this repair is CEL/Codes)
1 Pair Snips/Scissors


*** BE SURE TO DO THIS WITH A COMPLETELY COLD ENGINE ***


Click the image to open in full size.
Here are some, not ALL of the tools I used. I had to add tools as I went further into the job not really knowing exactly what I'd need. However these are the essentials to start out with!

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Step 1: Remove the engine cover pieces outlined in YELLOW by hand. They simply lift up and off.
Step 2: With a Phillips screwdriver - Unscrew the pop-up plastic screws and remove the engine covers.
Step 3: Remove 3 metal screws on the coolant reservoir tank with a Phillips.
*** Step 2 & 3 Outlined in RED ***

Step 4: Once coolant reservoir is unscrewed, carefully lift tank off of metal holding plate and located the sensor wire connected to the bottom. With a flathead screwdriver, being careful not to break the clip, disconnect this sensor and move the coolant reservoir out of the way. (Side note: At this time, I also removed the black engine cover on the side of the valve cover/side of manifold. Be sure to remove the oil cap before lifting up on this cover (after unscrewing 2 pop-up plastic screws just as in Step 2 above. Replace the oil cap once cover is removed.)

*** OFF TO THE PASSENGER SIDE NOW ***


Click the image to open in full size.

Step 1: Remove/unclip the four (4) connectors to your two (2) ICMs (Ignition Control Modules). (Circled in Yellow) Simply push down on metal clip and slide off connector.
Step 2: Unclip two (2) clamps connected onto your fuel lines (Circled in Cyan/Baby Blue)
Step 3: Remove MAF housing from Airbox (Circled in Dark Blue) - there are two of these clips directly Left & Right from each other. Don't lose the O-Ring inside!
Step 4: Unclamp the Airbox's clamps (4) that connect the Top & Bottom of the Airbox together (Circled in Lime Green). The 4th is on the MAF housing corning, down below. Hard to reach.
Step 5: Now with your large pliers (or similar tool), remove the accordion hose from the silver Y-pipe. Squeeze the clamp together and it will open up, allowing you to slide off the hose.

Next to the accordion hose, this is where you will now see three (3) of your four (4) connector harnesses with connectors for the Oxygen Sensors.
Click the image to open in full size.

*** REMOVING Y-PIPE ***

If you are like me and do not have any spare 1-time clamps lying around, I came up with another method to remove the Y-Pipe and never have to worry about tampering with those clamps.
Click the image to open in full size.

Step 1: Remove three (3) 10mm bolts located near the rear of the Y-Pipe, near where you just removed the accordion hose. Next, follow the Y-Pipe down to where it splits and heads down the side of the manifold. Next to your Coil packs 1 & 4 (near the front of the engine) you will see two more 10mm bolts. Remove these. All necessary bolts to be removed are circled in RED in the above photo.
Step 2: Head back to the rear of the Y-Pipe and you will see part of the Spyder hose assembly connected to a little off branch next to the curve in the pipe. It is black and plastic. Squeeze down on the top and bottom of this and pull it off.
Step 3: If you have already replaced your DVs (Diverter Valves), you probably already have reusable hose-clamps installed. Using a flat head screw driver, loosen these hose-clamps and remove the black tubing from the Y-Pipe, from the DV. (Circled in GREEN in the above photo).

Your Y-Pipe should now be free to be removed. Your engine should now look like my photo below.
IMPORTANT: TO ENSURE NO DIRT/DEBRI/ETC GETS INTO ANY UNWANTED PLACES, USE CLEAN SHOP RAGS AND COVER OF HOLES OF THE PIPING YOU JUST EXPOSED FROM REMOVING THE Y-PIPE!!

Click the image to open in full size.


Now that you have everything needed to be removed out of the way (Coolant reservoir, Air box, MAF housing, Accordion hose, Y-Pipe), using your flashlight you should be able to see the passenger and driver side O2 sensors. First we will go over the passenger side as it is easier to remove then the driver side.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Remove the Passenger Side Pre-Cat Connector from its retaining harness by sliding it forward and out. Once removed from the harness, depress the two clips and slide the two connectors apart shown below:
Click the image to open in full size.

Spray and SOAK that baby with PB blaster. The angle is a little hard, but after a few short, gentle sprays, you'll be able to determine exactly how to spray it where the sensor meets the bung of the CAT. Allow it to soak for 10-15 minutes if your sensors are older (mine had 115k miles on them. They weren't going anywhere!) You may want to repeat this step a few times depending on age.
Click the image to open in full size.
Click the image to open in full size.

Now with your rig'd tool (O2 wrench, Universal, 2 foot extension, ratchet) that is securely taped/tied together (you do NOT want to drop anything down below and at this angle, it is very easy to lose your O2 wrench/crow's foot! Better to be safe than sorry!)) slide it over the O2 sensor wire and down onto the sensor. If you aren't able to loosen the sensor with some elbow grease/muscle, try the old mechanic's method of tightening first, then loosening. Or you may try what I did and get a rubber hammer and pound away at the ratchet knocking her loose. It is easier said than done, be warned! To get off my passenger pre-cat, I probably fought with it for a good hour or so!! Once she comes loose, reach down and hand loosen her off. Your retaining clips should already be cut - just pull the sensor up and out.

Apply anti-seize to the threads of the new sensor, reach down and hand tighten her. Be careful not to twist the wires of the new sensor while doing so! I used my left hand to turn the wires as I tightened the sensor with my right hand. Get your rig tool again and give her a good nice tighten - doesn't have to be extremely tight, you don't want to fight her as much next time as you did this time if she needs to be replaced again! Re-thread the wire the way you feel is best, applying zip ties along the way. Try to stick to the OEM setup for best results. Attach the new connector-sensor end with the connector-ECU end, reinsert both connectors into their appropriate harness and congratulations, you are now done with the passenger side!

Now onto the PITA driver side. We do not lie about this…this sensor, due to it's angle and limited availability on the 2.7L engine puts the ITCH in BITCH. ROTFL.

Click the image to open in full size.

Click the image to open in full size.

Sorry the picture is out of place but this (circled in YELLOW and RED) are the pieces of the Spyder assembly I was referring to above that were disconnected.

Click the image to open in full size.

The hardest part of removing the driver side O2 Sensor is it's angle. If it wasn't for that, it wouldn't be so bad. However, I, as well as many others, agree it is best to approach it from the passenger side of the engine bay, using your 2 foot extension, universal socket and O2 wrench/crow's foot. This sensor honestly took me a good 2-2.5 hours to get off! It got drenched in PB blaster for 20 minutes at a time, for about 5 times! I honestly kicked, cussed, cursed and threw a tantrum trying to get that sucker out. Do some breathing exercises to calm yourself before attempting this one! loll

This side is done the same as the passenger although below the connector you have a heat shield with two buttons that needs released, and 2 retaining clips that need cut. Once loosened with the wrench/crow's, again, hand loosen the rest, and carefully pull the old sensor out. Anti-seize the threads on the new sensor, hand tighten her down, then grab your wrench/crow's, like the passenger, tighten her down, rethread your wires, applying zip ties in factory location or some where close to, connect the sensor connector with the ECU connector, reinsert into the harness housing and give yourself a great big pat on the back! The two hardest sensors are complete.

Click the image to open in full size.

As most here say - reinstall everything in the reverse order. Again, congratulations on a job well done!!!

Last thing's, last. If your old O2's were throwing a code, hook up your VAG-Com/OBD II Scan Tool, erase the code(s) and remember to take her on a drive cycle so the ECU can relearn all of it's 9 categories with the new sensors! Even if you weren't throwing codes, this is still a good step to complete.


Now, even though I have not done my post-cat's (I ordered them at the same time to have them as back-up, plus got a wonderful deal on them from amazon.com - but I will worry about doing these when the weather is a bit more kind.) the process is the exact same - only EASIER!! I bet that put a smile on your face. The only difference being these are located after the cat-converter and must be attained from underneath the vehicle. If you are doing these at the same time as your PRE's, just add a jack lift and two jack stands to your list of tools needed. PLEASE if you are unfamiliar with the proper way of lifting a car, refer to your OEM Manual AND/OR the Bentley Publisher's manual. Always secure ANY vehicle with the parking brake applied, blocks in front of/behind of the rear tires and ensure that the vehicle is safe and sturdy before EVER climbing underneath one.

I truly and honestly hope this HOW-TO Tutorial has and will help many of you in the future. I have just spent the last 2.5 hours preparing the pictures, and writing this tutorial - I thank all of you that has ever helped me in the past and am always happy to provide back to our little community of Audi Worlders

Good Luck & God Bless!


- Ben - (01A6Turbo)
i was trying to check my sensor on passenger side and they where all reading over 14 (ohms) my gas mileage is terrible right now
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Old 03-27-2010, 11:59 AM   #9
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Default how to check 02 sensor

i was trying to check my sensor on passenger side and they where all reading over 14 (ohms) my gas mileage is terrible right now
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Old 03-27-2010, 12:00 PM   #10
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oh and i have 2000 S4
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Old 03-29-2010, 05:51 AM   #11
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I would just add - there is probably no need to remove the Y pipe or the top half of the air box.

Just remove the covers, the MAF and associated flexable pipe and the auxiliary air hose.

The whole job should only take about 1 hour for both - once have done them a couple of times!
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Old 04-11-2010, 01:02 PM   #12
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Thank you so much for creating this tutorial - it's going to save me a ton of frustration! You rock!
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Old 04-12-2010, 05:01 AM   #13
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Quote:
Originally Posted by Shamgar View Post
Thank you so much for creating this tutorial - it's going to save me a ton of frustration! You rock!
lol you're welcome my friend
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Old 11-20-2010, 09:08 AM   #14
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Great tutorial. I got mine done in about two hours and no more check engine light!

Thanks
Mike
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Old 11-21-2010, 11:56 PM   #15
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Wow, this seriously will come in handy when I need it. A job well done. I also like the fact that it's a TIP as well. Some things are different from the TIP to the Manual as you guys already know.
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Old 12-31-2010, 11:33 AM   #16
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I got everything done but installing the new O2 sensor on the pre-cat driver side.. wow PITA is a wild understatement. I can't even get the new one in there. Theres no wiggle room whatsoever and even for a guy with smaller wrists it seems impossible. You guys had to have removed some more parts/hoses to do that part, didnt you???!?
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Old 02-26-2011, 03:19 PM   #17
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Thanks for doing this write up, came in handy today as I changed my pre cat sensors. Passenger side took like 15 minutes to remove and replace. The drivers side about 15 minutes to remove, but I will be damned if I can't get the new one back in! Not much room in there to get a grip on the sensor to get any turns on it. I event tried using a 2 foot piece of rubber hose with the sensor stuck in the end but couldn't get it started. Any tips out there? I have a 2001 A6 2.7T just like this thready. I walked away after an hour and figured would get back at it in the morning.
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Old 02-27-2011, 07:48 AM   #18
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Well, I went back at it fresh this morning and was able to get it started by hand after stretching my arm down as far as I could possibly go. Once the threads got started, the O2 sensor tool made short work of getting it tightened up.
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Old 12-12-2011, 07:07 PM   #19
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Just wanted to say thanks! Did the passenger side pre-cat today.

Attacking it from the right angle makes all the difference.
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Old 06-02-2012, 11:32 AM   #20
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I have performed this operation twice now, specifically Bank 2 sensor 1 drivers side pre cat. Neither time did I remove the Y pipe or some of the other parts you removed.

I remove the screws for the coolant reservoir and move it out of the way but leaving all the hoses attached. I pull the O2 connector and the wire/connector next to it on the fire wall out of the bracket and move them aside. Unsnap the heat wrap around the wires so you can remove the O2 sensor/wire. This gives ME (if you have bigger forearms you may be hampered) enough space to reach down and slide the crows foot over the sensor. I then use a combination of extensions with a u joint and wobbler on the end, you can almost get a straight shot from the passenger side if you put the extensions between the two hoses just above the sensor and in the line of site from the passenger side. Follow the instructions to douse with PB break (I have yet to find anything better) I also start with a cold car but run it for about two minutes to put some heat into the manifold to help free the sensor. Once free, I use the wire itslf to spin the sensor out of the bung with a little help from my hand.

I have also used the universal Bosch O2 sensor which you have to splice into the oem plug of the old sensor, it is both simple and robust and will save you in the neighborhood of $50.

Hope this helps.
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Old 06-02-2012, 11:32 AM
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2004, audi, b5, back, check, diy, install, lambda, o2, oxygen, replace, s4, sensor, squeze, unscrew


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