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MJK1
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Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Thu Aug 15, 2019 5:17 pm    Post subject: Persistent 997.1 C2S engine fault codes Reply with quote

I have the following 3 engine fault codes keep coming back every couple of hundred miles. I’ve replaced the upstream bank 2 oxygen sensor but it’s not stopped the P0153 code. Anyone any idea what the problem could be?
 



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alpinaman
Montreal


Joined: 21 Feb 2012
Posts: 563



PostPosted: Thu Aug 15, 2019 5:53 pm    Post subject: Reply with quote

AOS letting unmetered air into inlet manifold ?
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7161
Location: Brighton


PostPosted: Thu Aug 15, 2019 6:02 pm    Post subject: Reply with quote

As long as there are no other fault codes listed .. ie tank vent then you have a leak in the exhaust ..

air is being drawn in and its registering a lean mixture on this sensor .

Check for blows close to this sensor .. perhaps a hairline crack .

Secondary air is an air pump that blows air into the exhaust from cold for 30 seconds to fast warm the cats .. its not working !
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MJK1
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Joined: 03 Nov 2018
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Location: Church Broughton, Derbyshire


PostPosted: Thu Aug 15, 2019 10:16 pm    Post subject: Reply with quote

That’s great thanks, I know of a slight exhaust leak but it’s at the joint between the catalyst and muffler on bank 1. I’ll have a look for others at the weekend and get them fixed.

If there are more than one unconnected problems, do they trigger fault codes at the same time? All these 3 codes always appear at the same time which I thought would mean they are connected.
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7161
Location: Brighton


PostPosted: Fri Aug 16, 2019 6:20 pm    Post subject: Reply with quote

Fault code details in the image below ..

You can see the 2 items it lists for this fault .. you have replaced the sensor so logically we are left with just an exhaust leak .

However .. that's not to say its not something else .. it's just so unusual that it was never listed on the fault code details .

Secondary air is not working at all as it lists a fault for both banks and not just the one with the lambda sensor fault .. this to me indicates 2 seperate faults .


The car tests the secondary air system by running it when the engine is at operating temp for a few seconds .. it looks at both bank lambdas for a lean mixture .. it then knows its working ok .. if it doesn't see this on both banks if flags a code .. which is what you have .

Logically its seeing something different on the single bank lambda sensor when driving hence the code is just for this bank , if linked then it should be both banks lambda sensor codes .

At work there's many different values from sensors i would be looking at .. here and i just have the fault codes so go by what they " suggest ".

Nothing to say the info is correct .. nothing to say they are not linked though ..

Basically .. if in doubt then fix the secondary air fault first then see if the lambda one comes back .


EDIT ..

On a single cycle from cold to hot then it would monitor and check both faults listed so yes it would flag both on a single journey .
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MJK1
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Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Fri Aug 16, 2019 9:41 pm    Post subject: Reply with quote

Thanks deMort that’s a great help. I’ve got a Durametric Diagnostic Software so I’ll see if I can get the Secondary Air Pump to work via the software. If it doesn’t, I’ll check it’s getting an electrical supply. If it is I guess it’ll be the pump. If the pump works I’ll check the valves and pipes of the secondary air system.

I’ll also have a good look at the exhaust and seal any leaks if there are any.
 
  
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MJK1
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Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Fri Aug 23, 2019 6:45 am    Post subject: Reply with quote

Update on this problem. I plugged the durametric in and activated the secondary air pump. It works and sounds like a vacuum cleaner. I then started the car and sure enough the pump worked for 1 minute 40 seconds. It helped knowing what I was listening out for. I did notice a strong smell of un-burnt fuel coming out of the exhaust during this time so I suspect there is a problem somewhere in the system downstream of the pump.

I’ve checked the exhaust and can’t find any leaks. The same 3 codes are still coming back every few drives. My next job will be to remove the air box, alternator and intake manifold and then try to diagnose which part of the air system is preventing the air getting through.

Any other ideas?
 
  
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99pFlake
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Joined: 24 Jun 2018
Posts: 48



PostPosted: Fri Aug 23, 2019 8:14 am    Post subject: Reply with quote

Maybe check the pipework for the secondary air pump? I had a similar fault after the engine of my Phaeton was taken out (air pump running but fault still showing) but it was because someone hadn't properly clipped the pipe back onto the pump (and it was so stiff it had to be sworn into place...)
 
  
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MJK1
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Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Fri Aug 23, 2019 10:42 am    Post subject: Reply with quote

Yes I’ll be checking all pipework and the valves. I’ve just bought a hand vacuum pump off eBay to help with identifying where the problem is. This appears a useful link to help with trouble shooting.

https://cdn2.ms-motorservice.com/fileadmin/media/MAM/PDF_Assets/Secondary-air-system-Design-components-trouble-shooting_54338.pdf
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7161
Location: Brighton


PostPosted: Fri Aug 23, 2019 6:34 pm    Post subject: Reply with quote

This does seem to be a bit of a nightmare to be honest .. there's many values i would like to see .. i'll just humbly suggest an Indy has a look at this point as it may be the easiest solution .

Either way i'll run through what i think atm .. this might get complicated .. sorry .

You said every few drives .. do you know how many ? .. basically a fault with secondary air should logically be thrown up every cycle .. cold to hot running .. say 10 miles .

Lambda sensor or emissions related faults often take several cycles to flag a fault .. i tend to say 4-5 for a fault to be reported ... if several cycles then it leans towards the lambda .

My confusion though .. if it was only codes for bank 2 then its a lambda fault or something related to that .. air leak , partially blocked cat , cracked exhaust .

Secondary air on B1 is a seperate fault .

What i'm thinking from this .. is B1 lambda almost at the point of triggering a code but not quite .. ie we have a running issue but atm only B2 lambda is throwing a fault code .

Values needed to have a clue ..

B1 and B2 .. rkat , Frau and Frou .. your tester may indicate them as adaptations idle , mid range and max rpm .. its the fuel adaptations the car has to make to maintain lambda on each cyl ... ( lambda its the correct air / fuel mix )

maf readings at idle .. kg/hr hopefully .

Watch the live readings from both bank lambda sensors ( engine hot and at idle ).. you should see a switch between 0.2 and 0.8 volts .. up down , up down .. do they switch at a similar rate .. if you have data logging then graph both and photo it please .

I need to know if B2 lambda is switching or staying lean ... if it stays at 0.45 then its dead or the dme is not getting a signal from it .

Fault code says dynamically inert .. that to me means its not switching .

secondary air pump is working .. it blows air through holes in the head into the exhaust manifold .. it's possible the ports in the head are blocked .. i can't see it and there's not much you can do about it but its something to bear in mind .

There is also a valve i think . not sure . you need to investigate that side .

So .. in essence , i'm thinking atm ..

Is the wiring from the lambda sensor to the dme all ok ..

Is the cat that side partially blocked ..

Is it actually a running fault but the other side is just about within limits.

Is there a crack in the exhaust , perhaps you can't see it .

Tank vent , carbon canister .. these affect both banks but it is listed in the code description .

Without looking at a lot of things , driving the car etc then i am at best guessing ..

What i will add .. if your keen and want to get involved then i might have some basic training info on these i can send you .. pm me an email addy if so and i'll see what i can dig out .

Many years searching the internet has found me the odd bit of info that's useful .. sometimes lol .

also just to say .. read this many times as there's a lot here to get your head around as after all .. your the one fixing the car and perhaps learning as you go .. welcome to my world Very Happy
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She's not going until july 2020 though .



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MJK1
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Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Sat Aug 24, 2019 7:05 am    Post subject: Reply with quote

Thanks for the detailed reply deMort, pm sent.
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7161
Location: Brighton


PostPosted: Sat Aug 24, 2019 6:28 pm    Post subject: Reply with quote

Sorted but post here instead of email if possible please with your progress .. it's nice to share Smile
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My Daughter's Crowdfunding has hit the target see Here

Thank you all so Very much .

She's not going until july 2020 though .



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Now At An Indy.
 
  
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MJK1
Newbie


Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Fri Aug 30, 2019 9:45 pm    Post subject: Reply with quote

Update - I connected the Durametric up tonight and started the engine. I recorded the engine speed and all 4 O2 sensor voltages for about 4 minutes.

The first graph shows the speed trace, when first started it goes up to 2000rpm and then settles at about 1100rpm for 80 seconds. The secondary air pump then switches off and it settles to 720rpm. Between 164 and 207 seconds I increased the engine speed via the accelerator pedal.

The second graph shows the upstream O2 sensor voltages for banks 1 and 2. I was expecting to see voltages between 0 and 1 volts but they are between -50.8 and -49.8 volts. The high voltage between 0 and 80 seconds when the secondary air pump is running I suspect is showing no secondary air is getting into the exhaust manifold. This was initially suspected so I'll investigate it further. After 80 seconds both sensors do switch between high and low but the rate of the bank 1 sensor is far higher than bank 2. I don't know the reason for this.

The third graph shows the downstream O2 sensor voltages for banks 1 and 2. These are between 0 and 1 volt except the bank 1 sensor doesn't cycle up and down. Does this mean this sensor is faulty?

DeMort, thanks for the previous help, is there anything here that stands out or is there anything else I should measure or look out for?

Last edited by MJK1 on Sat Aug 31, 2019 7:04 am; edited 2 times in total
 
  
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MJK1
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Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Fri Aug 30, 2019 9:46 pm    Post subject: Reply with quote

Engine speed after cold start
 



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MJK1
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Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Fri Aug 30, 2019 9:48 pm    Post subject: Reply with quote

Upstream O2 sensor voltage after cold start
 



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Upstream O2 sensor voltage after cold start
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MJK1
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Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Fri Aug 30, 2019 9:49 pm    Post subject: Reply with quote

Downstream O2 sensor voltage after cold start
 



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Downstream O2 sensor voltage after cold start
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7161
Location: Brighton


PostPosted: Sat Aug 31, 2019 5:35 pm    Post subject: Reply with quote

Ok .. interesting .. my thoughts ..

I have a feeling the secondary air system is working just fine .. you can't really check it via the lambda readings on a warm up first start and be accurate but the trace on the lambdas does seem to indicate that this system is ok ... it may not be but i want to ignore it for the moment ..

The voltage is just wrong for both sensors pre cat .. these are not wide band sensors and even if they were its still the wrong voltage so im guessing the tester is just displaying it wrong .. it's also at minus 50 ?? just wrong !

If not then you Will have fault codes for both pre cat sensors as they are basically not working according to the voltage .

the switch up and down is fine so i'm guessing it is 0.2-0.8 volts but bank 2 is very slow .. that is indeed an issue.

Its also the sensor you have replaced .. and yet its still slow .. interesting .. its not the sensor but something else that's cause a rich / lean normal operation .. but too slow ...

Something restricting the exhaust gases that bank perhaps Question

Post cat sensors .. again this tells a story ..

Bank 1 shows the cat is working ...

bank 2 shows the cat isnt working ..

The bank 2 sensor is switching rich/lean and i'm assuming this is on idle .. the cat is not doing its job and i suspect it might be damaged as well .. perhaps partially melted or indeed a knock at some point has broken bits off and parts have turned sideways thereby restricting air flow .

Your first point of call atm is to check the cat that side .. either a bore scope down the pre cat lambda sensor hole or just remove it and have a look .

That's my logic anyways and what i would be checking next on this rather interesting and difficult fault .

Quote from one of my previous replies .. seems like this was already an idea of mine lol

deMort wrote:



Is the cat that side partially blocked ..


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My Daughter's Crowdfunding has hit the target see Here

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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MJK1
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Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Mon Sep 02, 2019 1:19 pm    Post subject: Reply with quote

Thanks for the feedback deMort, I’m going to swop the O2 sensors for each bank over and measure the voltages again and see if the voltages swop with the sensors or stay with the bank. The parts list shows both upstream and both downstream sensors are common parts.
Depending on these results, I’ve also got a spare set of catalytic converters that I can fit to see if that makes any difference. I’ll report back with the results.
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7161
Location: Brighton


PostPosted: Mon Sep 02, 2019 6:20 pm    Post subject: Reply with quote

On the off chance you have a temp gun then check the temps of both Cats at operating temperature .. a defective cat will be colder than a good one ...

Ie ..

If the catalyst has stopped working, the front temperature will be about the same as or higher than the rear temperature.

In a good catalytic converter, the rear of the converter will be 20+ degrees hotter than the front.

if you have a spare then remove the old one and have a look .. i think if its faulty it will be obvious but fitting another will prove it .
_________________
.

My Daughter's Crowdfunding has hit the target see Here

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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MJK1
Newbie


Joined: 03 Nov 2018
Posts: 28
Location: Church Broughton, Derbyshire


PostPosted: Tue Sep 03, 2019 10:36 pm    Post subject: Reply with quote

This evening I swapped over the upstream and downstream O2 sensors. I then did a cold start and recorded the same parameters. As you can see below the results were practically identical. This confirms the O2 sensors are all working.

Next job is to swap the catalytic converters and see what difference that makes.
 
  
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