VCDS method of finding oxygen/lambda fault?

[Conan_the_Librarian]

I'm out of my depth here. I'll tip Ben off at AVP see if he will comment.

[Just_Ben]

Got ya PM Mike!

This is a definate issue with the CATS being of a different tolerance to Audi's own. The car will pass an MOT with flying colours even though it won't pass the car's own on-board emissions control checks.
The post CAT lambdas sole job is to monitor the condition of the CATS, the pre-CAt ones doing the job of fuel metering.
The CATS will jsut be not as good as Audi's original, therefore the only fix I have used in the past has been a mod in the engine ECU map. Usually you only have this issue on tuned cars so a map mod is simple and req'd anyway. The modified map just adjusts the sensitivity of the post CAT lambda's (or removes them if no cats are fitted!!)

Hope this helps - don't go spending on new Lambdas!!! You'll be wasting ya cash!

Thanks very much for your help Mike and AVPerformance

I've been reading around about the wayne angle blocks and those anti-foul sockets, figured that method is going to be the cheapest option to see if I can get the code to stay off for some length of time. I've got a couple on order (designed for the same purpose on hydrogen hybrid motors) for less than £20 - still cheaper than if I'd gone to audi/specialist for a diagnostic.

I presume that a remap is what you are suggesting AVP? I'd be interested if I was keeping the vehicle, but I just want to get it fixed up ready to sell now. I'll keep it in mind though as I can't sell a duff motor, unlike the guy who sold it to me...

Anyone in the market for an '02 S8 on 130k watch this space (still a few other jobs to finish yet)

[A8 Doc]

Foulers work a treat. Used them as a temporary measure on the M5 until I mapped them out

Well, I struggled to get the o2 sensors off, so I ended up taking the cat pipes off. Got one sensor off, fitted anti-fouler, refitted sensor no worries.

Next one, the sensor would not budge - then I noticed the guy who did the welding fitted the pipe & welded close to the sensor weldolet, so he's basically welded the sensor inside the weldolet. Had to break it out and chop it.

So, I need a new sensor and someone to tap the weldolet with a new thread, possibly even a new weldolet and pipe welding on yet, have to see how knackered the thread is.

The saga continues...

[Goran]

Ben, can the chip be re-coded to code out the post-cat lambdas?
I have had Wayne blocks on my car with 100cel cats for 2 years but have had some intermittent errors for the rear lambdas after the first year (but no CEL yet). I would like to just do away with those pesky rear lambdas.

I tried changing the engine code as per Tobes's instructions back on tyresmoke forums, but it wont take the code for Euro II. However it will take the code for a manual gear box for example, so perhaps the Euro II program isnt loaded on the ECU. Is there any other way to code out the rear lambdas without having to get a new chip?

Tobes' instructions:

"You need to select, Engine 01
then check the coding box,
This is the coding table

* ??xxx: Emissions
o 05 = Euro II/D3
o 06 = TLEV (USA)
o 07 = LEV (USA)
o 08 = GUS/China
o 10 = Euro III
o 11 = Euro IV/Japan
o 25 = South Africa
o 26 = Mexico/Taiwan
o 27 = Brasil
* xx?xx: Powertrain
o 5 = Front-Wheel-Drive
o 6 = All-Wheel-Drive without ASR/ESP (with CAN-Bus)
o 7 = All-Wheel-Drive with ASR/ESP (with CAN-Bus)
o 8 = All-Wheel-Drive with Post-Switch Stage (Low Range - A6 Allroad only)
* xxx?x: Transmission
o 1 = 6-Speed Manual Transmission
o 5 = 5-Speed Automatic Transmission (01V)
* xxxx?: Vehicle
o 2 = Audi A6
o 5 = Audi A6 Allroad

Write down the old code, The first 2 digits are whet you need, So if yours are 10 you need to change it to 05"

The above private message was as a result of this thread:
http://www.tyresmoke.net/forum/audi-...s-removed.html

Also, I was looking up lambdas on Elsawin, there is a bizzare statement on there that seems to indicate that rear lambdas take priority over front lambdas? I hope I havent affected fuelling by removing the rear lambdas out of the flow of the pipe. Seems a bit crazy to me I thought only front lambdas affected fuelling? (unless I mis-interpreted the upstream-downstream terminology)

Thanks

[briang9]

just been searching and found this post, has anyone found a successful solution to this? I have sports cats which seems to cause the Engine Management light to come on had it checked and its related to post cat sensors, I know the Laird got some extensions fitted to his but as its now Davids car and he had the same problem last weekend doesnt look like that worked long term either.

thanks for any help

cheers