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Discussion Starter #1
In the last 2 week I have had the same error code come up concerning Low secondary air flow which I thought would only throw a engine warning light in the US.
I have attached both screen shots from both errors. Please could someone advise on a possible 'FIX'
Thank you
 

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Best suggestion is take your vin to a dealer maybe a call will work and see if the DME has had a factory flash. Might have flashed it for the wrong country. It could also be that the OP had it flashed to a different update that was not intended for England. Some of the euro countries have it trigger the light. Was not required in England if yours is a right drive it is odd. You could just fix the problem as it is a real problem. SAP sys does have some benefits. I had that code and used tubing to bypass the heads and direct the air into the exhaust. Works sweet. You do need some fabricating skills.
 

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Sailor, this is what I was wondering about and was going to post this question, is it possible to by pass and just direct air to whatever the DME uses to sense the flow? I was thinking about doing what you appear to have done already.

So what and where does the DME use to sample air flow? Do you have any pictures of your set up? Thanks. I even thought about just blowing compressed air in there while it's cold to try to set the readiness code, not sure if it would work?

OP- hopefully I'm not hijacking your thread and this is useful to you too.
 

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Those don't fix the problem they just get around it. What I did was repair the system by routing the air through tubing to the exhaust.
I keep promising to do a proper thread on this but have limited time.
Here is the link. A little further up in that thread is another simpler way but you loose the belly pan, looks like anyway.
http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/128129-secondary-air-system-carbon-build-up-removal-pictures-post2773401.html
If you are really interested I would do a DIY on the repair I have some more pics.
 

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I posted those other solutions more as ideas for the OP to look at. I know they're more just kinda band aiding or masking the issue. But they'll get you by. However I am interested in a more long term solution that will keep the OBD 2 all looking pretty at state inspection time and not just scraping by with 1 one not ready code. I only just got the AA code a few weeks back on this car, I got lucky as it happened just after I did the inspection so have most of a year to come up with something. So I've only just started searching for the threads on this topic. I actually read the first few pages of the thread you linked there, and read about the de-carbon cleaning. I didn't get as far down it to see the by-pass solutions. So last week I had the idea about just by-passing it but did not see any threads on it. Glad to see it's been done but it looks more involved than I had hoped for LOL.

Thanks for the link. I think I can get a good idea of what needs to happen to make it work from it. But if you want to do a write up I'd love to see it. I understand about the time issue. I'm lucky to get time to read a couple of emails a day, nevermind write a tutorial LOL. I'm sure a few others would appreciate it too if you did a write up.

In a side note I used to do a lot of work on two stroke motor cycles when I was a teen (mid 1980's). They're very good at clogging exhausts with oily carbon due to the nature of them. Back in the UK they used to sell some chemical you could pour down the exhaust to clean out the carbon. (de-coking). I wonder if this would work to clean the SA passages? But may pit the aluminum if it got into the cylinders as I think it was pretty caustic? Just another thought.
 

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The chemical approach, a few ideas. Not sure if these will work on 4 stroke carbon build up as I think it maybe a bit harder? I'm thinking about trying the diesel on something though and see how it does?

Exhaust de-coke ?? - ADVrider
 

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Discussion Starter #8 (Edited)
Thank you all for the response.
Sailor if you wouldn't mind sometime doing a instructions for the bypass?that would be most helpful.
I also had these other 2 errors come up the past week or two.

I managed to stall the engine a couple of days ago, would this cause the Lambda error codes??
 

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These 144/145 (90/91) codes are caused by the AFR getting rich too quickly for the additive or multiplicative adaptions to correct so the quick-acting trim (lambda regulation) for each bank reached its limit of 0.75 trying to reduce injection times.

They're a bit of a mystery code but the usual causes for the rich running seem to be MAF's going bad or air/vacuum leaks. (I include the air/vacuum leak option against my better judgement :blink: because of recent discussions with sailor24 and a recent thread that found the cause for running very rich was vacuum leaks.)

You have INPA so can you post the Analogue Values 1 and 2 screens with engine at a hot idle?

Are you running an aftermarket MAF-less tune? They are more prone to setting this code because they freeze the adaptations for some reason.
 

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Discussion Starter #10
Thank you very much 68FB for your post much appreciated.
I have attached the Analogue Values for both 1 and 2. and also a vid of Analogue Value 2
 

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Discussion Starter #11
I replaced the MAFs a few months ago
 

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Discussion Starter #13
Hi I'm afraid I bought off ebay. Yes I shouldn't have. They were sealed Bosch units
 

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From your INPa data, the "total requirement HLM" (air flow) is low at 15.75 kg/hr which makes me suspect MAF's. It's usually around 19 kg/hr. But that could be largely because your "sucked air temp" (IAT) is so high. The engine temp is only 79C. Was the car sitting heat soaking for a while before you read these screens?

The fuel trims are all normal, good even, giving no clues as to why you are getting the 90.91 codes.

Did the new MAF's have the correct M5 part number on them?

Try using the F8 option to look at just the Lambda Integrator 1 and 2 (for faster updating) and driving around. You are looking for them suddenly getting down around the 0.75 level.
 

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Discussion Starter #15
Hi 68fb thanks again for you reply,
The bosch pt no. Of the mafs 0280217533

The car was ran to temp but left for about 15 mins before I ran the test.

I will also try your request and run the program whilst driving and I'll try to video the results and post them.
 

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Discussion Starter #16
I went out this morning this is with engine up to temp.

Lambda Integrator 1 & 2 only dropped slowly to the 0.75 level when going down hill with the foot off the accelerator.

the adaptive value 1 stayed around -0.00 and -0.01
and number 2 stayed around 0.02 and 0.04
 

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That doesn't look right. As you say, when coasting downhill, your pre-cat O2 sensor voltages go steady rich at around 0.75V and the lambda integrators (LI's) react by going to the lower limit of 0.75 to reduce the injection time. When coasting, my car does something completely different. The pre-cat O2 sensor voltages go dead lean at 0.00V and the LI's lock at 1.00V. The pre-cats going lean is to be expected as when coasting (foot off gas pedal) in gear above ~1200 rpm, the main throttle plates close and the IACV opens to allow some air into the engine to prevent high intake manifold vacuum which sucks oil down the valve stems and up past the rings. At the same time, the injectors stop injecting fuel. So the pre-cats see only pure air.
The LI's locking makes sense as there is no point them reacting and changing trims under this particular running condition.

But your pre-cats are showing rich, i.e. low oxygen content in the exhaust while coasting. And the LI's aren't locked but are reacting to the rich message and reducing injection times as much as they can.

I can't say I know why this is happening. One or more injectors on each bank leaking fuel when closed seems to be the most likely cause. (The plugs are still sparking while coasting so combustion will occur if there is fuel.) Another possibility is you have a messed-up non-stock tune. And I suppose it could be the IACV closing completely during coasting so that the pre-cats don't see any air/oxygen at all (which again would be more of a tune problem if there is no other indication of an IACV problem).

I'm not sure what to suggest for further testing. Do you have a prolonged crank after the car has been shut down for a while, with a puff of black smoke? Can you measure fuel pressure?

If this is just an occasional problem and it isn't causing you any grief, you could just ignore it.
 

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Discussion Starter #19
Hi 68gb when you say coasting do you mean with the clutch in? As in the clutch pedal depressed? The results was shown that the clutch wasn't pressed in.
The integrators slowly dropped to 0.75 over a 50 yard distance while the foot was off all the pedals so letting the car run down the hill under the engines power? I hope this sounds clearer as it's hard to explain
 

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Discussion Starter #20
I bought the car about a year ago. I don't know if it has any tuning done etc. the car seems to run ok and there is no loss in power as such but I don't really have another m5 to compare it to.
When engine is switched off it stops with no run on at all and no black smoke.
 
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