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  1. #1
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    Angry Audi a4 b5 problems any help would be great

    fitted a new o2 sensor as my car barely made it through its mot as it had high emissions

    change it took it to my garage and it had a fault code so he cleared it and told me it could be my cat as it has a hole in the down pipe and could be causing it to put the code on from there

    so my next step will be to change the cat

    he told me as well to change the coolant temp sensor as he said it could be telling the ecu that the coolant is only at e.g 14.c therefore making the car put more fuel in to compansate to heat it up more.

    the gauge on the dash is working fine tho

    took it back 3 weeks running now and the fault code keeps coming back.

    could anybody eles think why my car keeps on coding for the o2 sensor as its kinda bugging me lol

    thanks guys for any suggestions.

    scott

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  3. #2
    evilscotsman's Avatar
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    thats weird mate, how did it pass the mot with a hole in the downpipe? and the code, if persistent usually means the sensor or the wiring / fuse is / are faulty...did you crimp the connections properly or just bodge it with tape? Theres a 12v feed to the o2 sensor for the heater in it.

    The coolant temp sensor or CTS is separate from the one that drives the dash gauge. It would throw a code if faulty or way out of bounds but not if just reading low, did he vag-com it to see what the ecu thinks the coolant temp is?

    Overnight, the coolant temp should reach ambient - so scanning it cold is best to see if it matches the outside air temp or inlet air temp sensor when cold and not running. Need vag com or vcds of course.
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


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    Quote Originally Posted by evilscotsman View Post
    thats weird mate, how did it pass the mot with a hole in the downpipe? and the code, if persistent usually means the sensor or the wiring / fuse is / are faulty...did you crimp the connections properly or just bodge it with tape? Theres a 12v feed to the o2 sensor for the heater in it.

    The coolant temp sensor or CTS is separate from the one that drives the dash gauge. It would throw a code if faulty or way out of bounds but not if just reading low, did he vag-com it to see what the ecu thinks the coolant temp is?

    Overnight, the coolant temp should reach ambient - so scanning it cold is best to see if it matches the outside air temp or inlet air temp sensor when cold and not running. Need vag com or vcds of course.
    iv taken to the garage again today as i replaced the cat at the weekend and the down pipe

    the have put it on diagnostics and found bank 1 sensor (lamba) again

    hes cleared the code and look at the exsaughst and found the centre box to be a little noisy but nothing major aparently

    they then put it on emissions test and the hc are int he green reading 0.14 and the lamba and co2 are off the charts iv just put another post up asking people to help me as im not at a loose end and may resort to getting shot of the car febuary time if i cant find the problem

    the garage have now said to change the maf and the coolant temp sensor again and look for secoundary air leaks, you said that the coolant temp sensor are to seperate on my car would you car to give me some direction please every one please help me find a fix im going out of my mind with this car thanks

    and also i dont have vag-com or know any one with it could you point me in the direction of where and how i get it please sorry

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    evilscotsman's Avatar
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    no problem mate, look for a leak on the intake path, I posted on your other thread.

    dont change the maf unless you can get a cheap one but it is possible. Vag com leads are cheap as chips on ebay, chinese copys of course but the 607 and 409 ones are the ones to get, then download the free vag com from ross-tech.com and away you go, can do a good few things on the free version but its limited too, however rosstech will sell you a licence for $99 US (dunno what it is in our money, used to be 55 but will vary daily) then you connect a laptop to the car using vagcom (vcds) and theres lots of posts on using it to diagnose faults.
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


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    "Stick a V8 in it!"

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    You need to find out what exactly is wrong with the lambda. Vagcom will tell you exactly what is wrong with it.

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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    Quote Originally Posted by evilscotsman View Post
    no problem mate, look for a leak on the intake path, I posted on your other thread.

    dont change the maf unless you can get a cheap one but it is possible. Vag com leads are cheap as chips on ebay, chinese copys of course but the 607 and 409 ones are the ones to get, then download the free vag com from ross-tech.com and away you go, can do a good few things on the free version but its limited too, however rosstech will sell you a licence for $99 US (dunno what it is in our money, used to be 55 but will vary daily) then you connect a laptop to the car using vagcom (vcds) and theres lots of posts on using it to diagnose faults.
    that help is spot on could you tell me where abouts i should be looking for this leak in dumb dumb terms the guys at the garage were shuting up so as you can tell they wanna get out fast so info they were providing was very small but im starting to get my hope up if just bought a lead and downloaded the free software in a hope to get some results. cheers mate you have been a great help

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    Quote Originally Posted by aragorn View Post
    You need to find out what exactly is wrong with the lambda. Vagcom will tell you exactly what is wrong with it.
    im new to this software so can you tell me what i will need to do so when i get my cable i can jump in and go searching please thanks for you help mate

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    get it connected first, will undoubtedly be a faff as the computer may not choose the right port number depending on whether you get USB or Serial cable. get the right version as well, some only run up to version 401 IIRC, some guru will confirm no doubt

    fairly self explanatory.
    you just click on "engine" and run a search for fault codes.

    post up when you are done

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    Quote Originally Posted by jcb View Post
    get it connected first, will undoubtedly be a faff as the computer may not choose the right port number depending on whether you get USB or Serial cable. get the right version as well, some only run up to version 401 IIRC, some guru will confirm no doubt

    fairly self explanatory.
    you just click on "engine" and run a search for fault codes.

    post up when you are done
    haha brill yeah lets hope so ok mate i will post everything i can as soon as the cables come
    cheers mate

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    chinese sellers usually send a disk as rosstech dont supply anything but the latest version, however for code scanning you can get an autel vag405 hand held scanner like i got and its plug in, ignition on and press ok > follow menus

    65 on ebay, plugandplay keep in glovebox

    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


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    Quote Originally Posted by evilscotsman View Post
    chinese sellers usually send a disk as rosstech dont supply anything but the latest version, however for code scanning you can get an autel vag405 hand held scanner like i got and its plug in, ignition on and press ok > follow menus

    65 on ebay, plugandplay keep in glovebox

    OK PEOPLE WE HAVE CODES WHOOO KINDA LOL

    16518 - Oxygen (lambda) Sensor B1 S1: No Activity
    p0134 - 35- 10 - - - intermittent


    any help please guys would be great thanks all lets hope we can get this fixed

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    On the basis that you have changed the O2 sensor, it has to be a wiring fault i recon.

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    right iv been having a little play arround and found this

    when i remove the maf cable it comes up with that fault which is fine and another lamba fault but the no activity fault comes up

    the second i put the maf cable back in a clear all the fault codes the no activity fault comes back up

    am i right in beliving that the maf is dead and needs replacing.....???

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    more likely a faulty earth then...

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    Quote Originally Posted by Byzan A4 View Post
    more likely a faulty earth then...
    how does it earth then

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    Not sure as i have no idea what engine you have... LOL

    Probably a little brown wire under a 10mm nut/bolt around the top of the engine would be my guess

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    sorry lol its

    audi a4 b5 1998 1.8 non turbo se

    engine type ADR

    cheers mate

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    The earth is on the rocker cover under one of the bolts for the coil packs IIRC

  20. #19
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    when you unplug any component, a fault code will appear immediately, when you clear the codes, any fault still remaining will come right back mate.

    The MAF shares a supply and ground wire with other sensors but your car is non turbo so there arent many sensors on it cept the lambda probe, the maf and maybe an egr valve solenoid that share the same power and ground wires.

    The maf code came up because you unplugged it, and it ran in safe mode due to this hence the other lambda code appeared, the original fault is still there so the lambda has a wiring fault / intermittent connection issue but the others are not real as you caused them by pulling the maf plug off mate, the maf is probably ok but only vag com can determine if its flow measurement is correct or not, obdII codes are only generated for faulty or missing sensors, or readings that are way out of whack but not for wrong readings that still fall inside the full range of the sensor.

    Check the connections to the new lambda are good, clean, tight, only onto the copper wire core and not crimped onto the insulation (common fault when replacing them) or they haven't gotten burned off the exhaust at the joining point?

    The power and ground wires to the maf etc are continuous and loop from the ecu to the maf then on to each sensor in turn and terminate at the last one, the fuse is 25A red and located in the black ecu cabinet under the windscreen scuttle panel. I dont think you have a maf power or ground fault. Just chase the real code which is telling you the lambda is only making contact some of the time to the ecu hence the connections to the new probe wiring must be poor. Its nickel plated wire with high temp insulation so can be awkward to get a good tight crimp without care. Best way is to use either a heatproof ceramic connector block from an electrical wholesalers (ross, CEF etc) or inline crimp receptacles but they are pvc coated so only good up to 70oC therefore need to be tie-wrapped away from the exhaust system or wrapped with heatproof lagging.

    lol just noticed we have the same name.... always looks weird when you see your own name on someone else eh? I jumped out of my bloody skin in Tesco when some woman roars at the top of her lungs "SCOTT!!! Stop that right NOW!!!" and I look round to see some wee lad munching the pic-n-mix right out of the tubs.....
    Last edited by evilscotsman; 4th November 2010 at 12:45.
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


  21. #20
    "Stick a V8 in it!"

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    was it a cheap **** lambda or a decent bosch one?

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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    Quote Originally Posted by evilscotsman View Post
    when you unplug any component, a fault code will appear immediately, when you clear the codes, any fault still remaining will come right back mate.

    The MAF shares a supply and ground wire with other sensors but your car is non turbo so there arent many sensors on it cept the lambda probe, the maf and maybe an egr valve solenoid that share the same power and ground wires.

    The maf code came up because you unplugged it, and it ran in safe mode due to this hence the other lambda code appeared, the original fault is still there so the lambda has a wiring fault / intermittent connection issue but the others are not real as you caused them by pulling the maf plug off mate, the maf is probably ok but only vag com can determine if its flow measurement is correct or not, obdII codes are only generated for faulty or missing sensors, or readings that are way out of whack but not for wrong readings that still fall inside the full range of the sensor.

    Check the connections to the new lambda are good, clean, tight, only onto the copper wire core and not crimped onto the insulation (common fault when replacing them) or they haven't gotten burned off the exhaust at the joining point?

    The power and ground wires to the maf etc are continuous and loop from the ecu to the maf then on to each sensor in turn and terminate at the last one, the fuse is 25A red and located in the black ecu cabinet under the windscreen scuttle panel. I dont think you have a maf power or ground fault. Just chase the real code which is telling you the lambda is only making contact some of the time to the ecu hence the connections to the new probe wiring must be poor. Its nickel plated wire with high temp insulation so can be awkward to get a good tight crimp without care. Best way is to use either a heatproof ceramic connector block from an electrical wholesalers (ross, CEF etc) or inline crimp receptacles but they are pvc coated so only good up to 70oC therefore need to be tie-wrapped away from the exhaust system or wrapped with heatproof lagging.

    lol just noticed we have the same name.... always looks weird when you see your own name on someone else eh? I jumped out of my bloody skin in Tesco when some woman roars at the top of her lungs "SCOTT!!! Stop that right NOW!!!" and I look round to see some wee lad munching the pic-n-mix right out of the tubs.....

    Haha brilliant ok so basicly the lambda is good and I need to check the plug with a multimeter and check the plugs and fuse at the ecu to make sure there all good and if there's a break in the wiring to put new wires in. But if there's no breaks what would you suggest then thanks for your help mate you've been great source of info

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    Quote Originally Posted by aragorn View Post
    was it a cheap **** lambda or a decent bosch one?
    It's a ngk lambda cost 30 so yeah cheap I was thinking of going to way side audi and buying one of there Bosch ones as the tech at wayside said it could be because the car is programed to really understand Bosch ones and not really any otherw may and said I'm not saying it won't work just it will work better with what it's designed with so I was gonna but one from them next month but befor that I'm gonna check all the wording tonight and see where that goes I will post more infor later once iv had a look thanks

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    "Stick a V8 in it!"

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    NGK is an alright make though. Was it a universal one?

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    Quote Originally Posted by aragorn View Post
    NGK is an alright make though. Was it a universal one?
    I think so yes lol

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    is the wiring correct? sometimes the same colours are used on universal ones but they dont have the same function per colour as the oem one, you need at least heater B+, ground, and signal, some have a 4th signal ground too. Like say the car's white wire may be heater supply to the lambda, but the probe you bought may use white as signal etc, some sensors seem to work but behave oddly if wired up wrong. i.e the ecu "reads" the heater element resistance instead of the lambda signal voltage / resistance and may appear to the ecu as working sometimes and not other times depending on the changes in resistance as the engine warms up? Just a thought
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


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    ok guys so iv been having a little look around cleaned the earth was not to bad took a multi meter to the lambda plug and there is power and that seems to working ok iv taken the battery off for half an hour to reset the ecu after iv deleted the codes. when i put the battery back on and started the car the pic above in the red had numbers in it and the car was running nice then about 10 secs later started to drop and went to zero then the code for non active lambda came up so im guessing that the lambda is not right for the car so i will be buying one from audi at the cost of 134 ( if it works i dont care about the price im not gonna let this beat me lol) and i will hope that does the job it seems every thing is working electronics wise had a look at my fuse box there all good (and i dont have any fuses in the ecu box under the bonnet) so yeah any other ideas or shall i just go for the lambda from audi the ones in blue are ones that keep going up and down but they do that even if i remove the lambda plug so i have no idea what thats watching lol thanks guys your info is brill and is helping a lot so solve this
    Last edited by Crazymoesizzle; 6th November 2010 at 16:15.

  28. #27
    "Stick a V8 in it!"

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    You can buy the direct fit bosch lambda for about half that price.

    Just Lambda, Audi lambda sensors, Bosch and NTK zirconia and titania sensors by post

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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    Quote Originally Posted by aragorn View Post
    You can buy the direct fit bosch lambda for about half that price.

    Just Lambda, Audi lambda sensors, Bosch and NTK zirconia and titania sensors by post
    thats brill mate thanks but they dont have my engine code
    Scott 1998 Audi A4 B5 1.8 S E 5 Door Saloon

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    A4 1.8 quattro [8D2; B5] ADR 11.94-12.98 Front 4 1010 0258003478

    although it says quattro its the right engine code

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    Quote Originally Posted by sam80quattro View Post
    A4 1.8 quattro [8D2; B5] ADR 11.94-12.98 Front 4 1010 0258003478

    although it says quattro its the right engine code
    true well ill give that ago thanks mate ill have to wait though till end of month car taken all my money lol cheers dude
    Scott 1998 Audi A4 B5 1.8 S E 5 Door Saloon

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    Ok guys Ive taken some readings on the lambda sensor now and Im having doubts that the lambdas at fault anyways here what I have.
    Plugged in
    From the brown earth at the plug to the cars earthing point under the coolant tank and battery neg terminal.
    0.53v
    From the lilac to the red its (lambda sensor)
    0.84v
    From the red to brown its heater
    13.18v
    All the readings i have taken are all static they dont move or anything
    So what you thinking guys give me some ideas or somewhere or something to look at lol thanks
    Scott 1998 Audi A4 B5 1.8 S E 5 Door Saloon

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    "Stick a V8 in it!"

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    I'm not really sure i get what you mean.

    There are four wires on the lambda sensor, two are earths, one is power to the heater and one is the signal.

    What wires do you have at the sensor itself, and what wires are present at the car side?

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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    Quote Originally Posted by aragorn View Post
    I'm not really sure i get what you mean.

    There are four wires on the lambda sensor, two are earths, one is power to the heater and one is the signal.

    What wires do you have at the sensor itself, and what wires are present at the car side?
    no iv looked deeply into this ha ummm basicly i have four cables going in to the lambda first one is white and secound is white which does the lambda heater and earth and the other is black the signal to the lambda and grey is the other which returns the signal back to the ecu but what i posted below gives a reading of what they were all doing as i know theres ment to be some variation on the volts on the signal so it shows its working but mines just sitting at 0.84v and not moving so i have no idea lol
    Scott 1998 Audi A4 B5 1.8 S E 5 Door Saloon

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    Looking at the wiring diagram for the original sensor:

    Function, Sensor Colors, Car Colors, measurement
    Heater Live, White, red/green, ~14v
    Heater Earth, White, brown/green, ~0v

    The other two are less clear, but i think they're like so:

    Lambda Signal, black/white, red, cycling between 0v and 1v
    Lambda Earth, Grey, lilac, ~0v

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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    Yep, sounds like you've identified the right wires, just make sure they match up with the right ones on the car loom...

    0.84v solid suggests the mixture is rich, so either the sensor is fine and something else is causing it to be rich, or the sensor is duff.

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    Quote Originally Posted by aragorn View Post
    Looking at the wiring diagram for the original sensor:

    Function, Sensor Colors, Car Colors, measurement
    Heater Live, White, red/green, ~14v
    Heater Earth, White, brown/green, ~0v

    The other two are less clear, but i think they're like so:

    Lambda Signal, black/white, red, cycling between 0v and 1v
    Lambda Earth, Grey, lilac, ~0v
    i have mate look below you will see what i found
    Scott 1998 Audi A4 B5 1.8 S E 5 Door Saloon

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    Quote Originally Posted by aragorn View Post
    Yep, sounds like you've identified the right wires, just make sure they match up with the right ones on the car loom...

    0.84v solid suggests the mixture is rich, so either the sensor is fine and something else is causing it to be rich, or the sensor is duff.
    well i was thinking as the volts were static that it could be a sensor problem as when i unpluged the sensor with the engine running i had no volts on the plug which is understandable so im gussing maybe the sensor is at fault what does any one eles think iv checked the wiring all the way back to the ecu and can see any problems there. im mean the only other thing i can think of is my ecu is fried as iv been searching on the internet every minute of the day found an audi tt with the same problem and he said that his ecu was fried replaced it and the code disapeared so what youguys thinking im kinda at a stand still now as i dont know what else to do.
    Scott 1998 Audi A4 B5 1.8 S E 5 Door Saloon

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    ok, with the ignition on or engine running and the plug disconnected from the lambda, you should be getting 12 to 14 volts between the brown/green and the red/green wires coming from the car, this proves the heater supply is good.

    Next, with the lambda connected and the engine running (warm preferable so its in "closed loop" mode) you should be getting same on the green stripe wires as before, but now there should be 1v approx between the red and lilac wires, proving the lambda is sending a signal to the ecu, as Aragorn says if this voltage is still stuck at less than 1v its either a bad sensor or rich running, like an injector dripping fuel into a cylinder, a clogged air filter, bad maf reporting high airflow at idle, or some more obscure fault I cant think of right now (just off 12 hour nightshift lol brain dead)

    The lambda varies over time during warm up and in response to throttle increase, like when you rev it there should be a drop in the signal briefly until the engine settles at a steady speed or idles, then it will go to around 1v and stay there, it only varies if the air/fuel varies which normally only happens on acceleration or deceleration (rich on accel, lean on decel)

    You could log it in vag com over 10 or 15 minutes driving (lambda signal voltage) where it will be clear what it does under various conditions.
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


  40. #39
    "Stick a V8 in it!"

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    The lambda should never just sit at 1v, unless your at full throttle.

    1v means "off the scale rich"

    Under normal closed loop running, the lambda will constantly bounce between about 0.2 and 0.8v. This is because the sensor isnt particularly accurate, and has a very narrow band for most of its range, so the ecu continually leans off the mixture until it drops to 0.2 then richens it up slightly until it gets to 0.8. This doesnt affect the running of the car, because the difference between the 0.2 and 0.8v is very small in terms of AFR.

    The only time the sensor should sit pegged at the top end is at full throttle (well, large throttle openings), and the only time it should sit at 0.2 or below is on overrun where no fuel is being injected.

    I'd be trying a new lambda, or even refit your old one and compare the readings.

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  41. #40
    evilscotsman's Avatar
    Space Cowboy

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    ah cheers mate, my lambda knowledge is sketchy on the operating signal levels as ma head is full of diesels lol

    I knew it swung between 2 values on throttle and overrun but should have read up more before posting values, the wiring is well known but the signal volts quoted never stick in my mind. I was going on the assumption he will be under the car measuring so trying to think of what he'll get on his own while it was idling.

    I hate petrols
    B4 TDI - old skool project / daily driver...if it ain't broke, it's probably an Audi...


 

 
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