# Where is the Lambda sensor(s)?



## Dino_Donis (Apr 19, 2004)

My engine management light came on yesterday and I read the following codes out:-

17524 Oxygen(Lambda) Sensor heating B1 S1: Open Circuit P1116-35-00
17511 Oxygen(Lambda) Sensor heating B1 S1: Performance Too Low P1103-35-00

The car seems to run fine but don't want to drive it unnecessarilly until i have it sorted..

I take it the "B1" = Bank 1 & "S1"=Sensor 1 i.e. Front sensor??

Questions:-

1] Is it easy to change myself? 
2] Whereabouts is it? Any photos diagrams?
3] How much does the part cost?
4] What is the part number? (2001 BAM Engine)
5] Is it a dealer only part?
6] Anything to watch out for?

Thanks in advance...


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## barton TT (Nov 13, 2004)

I have that fault on mine went over to APS on friday they said it was fine to use the car until they can sort it.the part is about £60 and 1 hours fitting charge.also my g40 sensor needs changing as well.


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## Hallyfella (Mar 5, 2007)

The Lambda sensors are under the car in the middle section, there are two pre Cat ones and Two post Cat . 
they can be changed yourself but the pre Cat ones are a little arkward to get at, IIRC you will need a 22mm spanner.
They have wiring with a block connector that is housed inside a black plastic box(where all 4 plug into the wiring loom of the car).
A little word of caution for you, i had these fault codes flash up with the engine managment light and got the senors changed , two days later the fault was back on.
Eventually it was discovered that my main wiring loom under the car had an ingress of water causing the faults to flash up.
The loom needed replacing at a cost of £2k for a new loom or the another way was to re wire the sensors and bypass the faulty part of the loom . Guess which one i opted for ! :roll: 
Hopefully yours should just be the sensors. Dont buy the cheap ones either go for the Bosch ones if you can.

heres a link might help you.
http://www.gendan.co.uk/oxygen_lambda_s ... _1.8i.html


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## Dino_Donis (Apr 19, 2004)

Thanks for the replies...

OK so the pre-cat one is tricky to get to! Do I access it from the engine bay or do I need to put the car on ramps and get to it from underneath?
Is it on the manifold or exhaust pipe?
I take it I need an open ended spanner because of the wiring?

Thanks....


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## Bikerz (Aug 23, 2008)

You have a 225, so you only have 1 after the cats. This doesnt matter as all it is there for is to make sure cats are working (ie. the fumes are cleaner than when they went in to the cats) I have a decat so mine brings up thoose fualt codes, but its nothing to worry about, doesnt effect fueling or anything


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## Wak (May 6, 2002)

Dino_Donis said:


> Thanks for the replies...
> 
> OK so the pre-cat one is tricky to get to! Do I access it from the engine bay or do I need to put the car on ramps and get to it from underneath?
> Is it on the manifold or exhaust pipe?
> ...


A 225 APX has 1 pre cat ( access from engine bay )
A 225 BAM has 1 pre cat (access from engine bay) and 1 post cat ( under car)

Either way your B1 S1 fault is the pre cat sensor.

remove engine cover trim.
remove the strut brace.
disconnect main metal charge pipe and remove it or move it aside
release the charge pipe holding bracket, makes it easier.
Look down the back and you'll see the lambda in the downpipe

You'll need some tools to release it and you can trace back the loom to the connector.


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## Dino_Donis (Apr 19, 2004)

> A 225 APX has 1 pre cat ( access from engine bay )
> A 225 BAM has 1 pre cat (access from engine bay) and 1 post cat ( under car)
> 
> Either way your B1 S1 fault is the pre cat sensor.
> ...


Thanks Wak...Yes mine is a BAM engine and has 2 which is what I suspected...

I just been out and had a look and can now see both the lambda sensors, The one in the engine bay seems mighty tricky to get to and yes I can see that I would need to remove all the pieces you mentioned.
I'm debating whether to do it myself mainly because i need to get the replacement part which wont be until tomorrow and so wont have much time. Looks like I would have to let the engine cool right down also as I assume that charge pipe is going to get hot.
Is the nut on the sensor 22mm? Is there enough room to get an open ended spanner in there or do i need something special?

Approximate cost from dealers?

My car seems to be running fine with this fault, does it effect the engine map/fuel mix? or is it purely for emission monitoring?
I guess i'm asking whether it is safe to drive the car with this error?

Thanks


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## Wak (May 6, 2002)

I would definitely stay off any hard acceleration, keep it light and cruise even if it feels ok, a failed lambda should make the ecu run things a little richer

This pre cat lambda is important, a small adjustable spanner can get in there and once you have broken the initial bite it will be ok to remove.


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## Bikerz (Aug 23, 2008)

WAK, seeing as you around, you havent said otherwise, but I was told by well known tunners that the 2nd lamba after the cats wasnt needed, this true? I have just unpluged mine and left the 2 fault codes that come up, that ok?


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## Wak (May 6, 2002)

Bikerz said:


> WAK, seeing as you around, you havent said otherwise, but I was told by well known tunners that the 2nd lamba after the cats wasnt needed, this true? I have just unpluged mine and left the 2 fault codes that come up, that ok?


2nd Lambda is there to measure cat efficiency, you need a custom map tweak to get rid of the DTC's or there are some options if you search google for "O2 simulator" to either space out the lambda or try an electronic simulator

Do you not get an engine management light?


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## Bikerz (Aug 23, 2008)

Yeah I get a warning light on dash. I have a P-Toque map, but they didnt turn the light off! Il have a google now, cheers!


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## s_jon (Sep 6, 2006)

Wak said:


> A 225 APX has 1 pre cat ( access from engine bay )
> A 225 BAM has 1 pre cat (access from engine bay) and 1 post cat ( under car)


Hi

I have an engine light and the fault:
17526 - Oxygen (Lambda) Sensor Heating: B1 S2: Open Circuit
on my vagcom,

I have the earlier 180 engine (APY ?)

Could you confirm if it also has just the one Lambda sensor that I can access from the engine bay?

thanks John


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## kennyk (Apr 4, 2008)

Hi I have also 180T Coupe FWD, engine type is APP.
I need to change the front Lambda, can I access from the engine bay? If anybody has done the change, anything to watch out for?

Thank you,

Ken


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## Jurpo (Jun 24, 2009)

I did install new one like 2weeks ago. Same sensor is no longer available. Wire lenght in current part is 2X


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## Kristian_TT (Oct 31, 2006)

kennyk said:


> Hi I have also 180T Coupe FWD, engine type is APP.
> I need to change the front Lambda, can I access from the engine bay? If anybody has done the change, anything to watch out for?
> 
> Thank you,
> ...


+1


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## Diveratt (Aug 31, 2009)

WAKs thread is about right for the Pre cat, I did both mine last month. the new Bosch ones have a a longer lead on them but its no real problem. The one tool that will really help is a 22mm crowfoot spanner using a 22mm open end there is not enough room to tighten it up and you cant put a ratchet or a ring spanner on it as they dont fit over the plug.

Took less than an hour to do so no big deal.


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## finesse (Mar 3, 2010)

Sorry to bump up an old thread, I need to change my B1S2 sensor (post -cat) where is it and how difficult is it to remove the old one and replace?


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## coachvtt (Aug 25, 2009)

finesse said:


> Sorry to bump up an old thread, I need to change my B1S2 sensor (post -cat) where is it and how difficult is it to remove the old one and replace?


Located on passenger side, just before the rear tire, Located in a box. Mine was rusted on, took awhile with a bit of 
WD-40 or another loosening agent. Not sure since you all drive on the wrong side as well as the drivers side is
backwards then not sure which side it might be. Here in the states it's located pass-side just before rear wheel.
I have not changed mine due too I could not get it off and I'm cat-less and Maf-less with engine light!
Good Luck! Pre-cat is most important!


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## H4KSY (Aug 22, 2008)

I have the ECU light & an intermittent fault logged on S1 B1 (the pre cat sensor right?)

Am planning to change this myself & looking at this part from Euro's:

http://www.eurocarparts.com/ecp/c/Audi_ ... 70eb4&LAMS

PN: 710770425

Can anyone confirm that this is the correct part?

Also - it says "Part Info extra install work req;4 wire"

Anyone have an idea what this means? Im looking for some validation before ordering the part!!


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## phminiman (Sep 14, 2012)

Holy thread resurrection 

Having done this today, just worth mentioning how worthwhile it is to have one of these:

http://www.amazon.co.uk/Draper-Expert-5 ... B000MQ7XRA


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