Fault Code OBD II 0155 (O2 Sensor)
 

Ladies and Gents,

The only fault code I am getting from the A8 is in regard to the 02 sensors.

OBD II P0155 Oxygen Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)

Now this tends to come and go, I have days without the engine warning light on the dash. Then it pops back for a while to say hello then goes again.

Car drives fine, no problems and whether its on or not makes no difference to the driving of the car. That's all well and good but I would like to have it cleared so it stops annoying me!

Are we looking at here a case of a Lambda sensor swap, wiring or perhaps an exhaust leak (Though cannot hear anything)?

Aha, think I have found the reason.

Started up tonight and its sound quite fruity! Thought to myself this is not a sports exhaust so had a look.

A quick look shows that under the engine drivers side the exhaust I think Pre Cat has been wrapped with black cloth, looks like a cheap repair to me.

Anyone point me towards a diagram of the exhaust as I cannot quite tell if its the downpipe, cat or perhaps a flexible joint that's gone and will need to be replaced.

Here you go - top manifold in the first picture of the upper image and cat/pipe in the lower image

http://forum.a8parts.co.uk/attachmen...1&d=1361307838

http://forum.a8parts.co.uk/attachmen...1&d=1361307838



.

Good man, thanks for that.

Looks like number 3 on the second picture, where the bulge is I presume pre cat. Looks like one whole part to me also so the whole lot may need to be changed.

The bulge pre car is wrapped in black cloth so I think someone has done a little repair!

Anyone have the right part code as its time to work out whether to fix myself or see what ATS/ Kwik Fit would want to charge.

A little google and eBay suggests:

AUDI A8 Catalytic Converter Exhaust 90909 3.7 ltr 3/1999-2/2001

Last time I replaced a cat Kwik Fit were damn cheap so perhaps worth a quote at least.

Though does sound lovely right now +++

Down pipes from the manifold. Well obvious would be second hand parts give A8Parts a call and do it yourself if possible, ATS and the likes might be able to source pattern parts but get a quote first if that's the way you choose to go, as it could be time consuming. The flange nuts / bolts from down pipes to cats get hot, cold, hot,wet ect and rot, and flanges to the cats.
Manifold to downpipe is not too bad, inner arch out for access. It might be as cheep to use a local specialist exhaust that can bend some stainless tube to suit.

I will pop the old girl into the local Kwik Fit so they can get it on the ramp and at least have a look.

Get a quote and take it from there.

Part number for item 3 - RH side is -

part number 4D0 253 012 PX +++

But be warned its looking like about £860 on the parts prices I have and that may well be plus VAT :eek:

Try David or Carl at A8 Parts as they've had some 3.7's in there and may well have a 2nd hand one at much reduced cost

I am afraid there are no cheap aftermarket replacements available as far as I know. In your case as the cat is working fine it's probably best to cut out damaged piece of pipe and weld a new one in.

I did think that it might be a no no from one of the national companys.

I had trouble with the parts aft of the cats, the cats had been welded to the down pipes at some point and flanges welded to the cats, a bit of a mess. A local tyre and exhaust place has a tube bender and stock stainless tube (although not sure where they get it but i could stick a magnet to it) cut the section out and bent a bit of stainless tube to suit. I had some Flanges cut on the laser and supplied the exhaust place with these. Some were hole and some halfs, the halfs could be placed over the tube and welded together so the fluting didn't need cutting off and cause another problem.

http://forum.a8parts.co.uk/attachmen...1&d=1361349563

Its interesting I do a quick ebay search and find this:

http://www.ebay.co.uk/itm/3308472127...84.m1423.l2649

Now I could be missing the point here but are they not the same parts here?

Plus I will photo what i can and at least try and get it up on the ramp. I much prefer the thought of going to a proper exhaust company and getting something made.

Not 100% sure what you mean, do you mean in the picture?

The picture is showing 2 different views of the same pipe, 1 from the top (looking down) and 1 from the side.

Get a quote from a local but i don't reckon you'll get lot for under 100 notes.

Its amazing how clear the problem is when the car is on a ramp!

Went to Bells in Swindon, front Flex joint was gone and had been wrapped in tape! The other joint was on its way out also.

New joints all fitted and welded without having to replace anything else.

All in £200 +++

Result +++

Bells tyres and Exhausts are very good, they can fabricate stuff there and are pretty spot on most of the time +++ Glad you got it sorted, shame I didnt see you out and about - I was in my 8 around Swindon most of the day :)

Indeed, used Bells a few times with no complaints.

Had a couple of hours to kill and realised how bad Swindon town centre is these days!

lol most of it is being re-developed in various places at the moment, you should have popped in to the outlet village, a much nicer experience +++

Gents,

Still getting the engine light due to a dicky Lambda. Ran VAGCOM tonight and got the following:

Address 01: Engine
Controller: 4D0 907 558 AB
Component: 3.7L V8/5V G 0002
Coding: 11753
Shop #: WSC 00481
WAUZZZ4D73N002184 AUZ7Z0B2123267
1 Fault Found:
17539 - Oxygen (Lambda) Sensor: B2 S1: Internal Resistance too High
P1131 - 35-10 - - - Intermittent
Readiness: 0010 0101

Can anyone confirm the placement of B2 S1 and also will any old 4 wire lambda do? or do I need a special magic Audi gold plated one?

Put a new lambda in and the fault code returned a couple do days later which was annoying.

Though interestingly changed all the spark plugs and no fault codes so far!

We shall see if this has actually fixed the problem or just will return again in a few days time.

Arse :mad: