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Codes suggestions: Knock bank 1, lambda bank 2?

5K views 35 replies 7 participants last post by  putty_thing 
#1 ·
Hi all,

Good news! My M5 is back up and running, bad news, it's throwing some codes. Still, I'd have nothing to do on the evenings and weekends if it didn't.

From the look of the codes, I've got some issue w/ both lambda sensors on bank 1 and knock on that bank, and then fueling issues on bank 2.

Could the two be related? I'm wondering if the lambda sensors haven't been connected correctly - the car was in a not-so-great-as-it-turns-out shop recently. If the lambda is out, I wonder if that's leaning out the mixture on bank 1 enough to cause the knock.

Guessing the fueling on bank 2 is a vacuum leak, but could it be caused by the issues on bank 1?

INPA output below, thanks for any hints!


 
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#2 ·
Can you post your fuel trims from INPA as well? That might give more clues. Your guess on the vacuum leak could be correct. You can do a visual check of the fuel pressure regulator hose attached to throttle body #7. It is a problem area on bank 2 for air leaks.
 
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#7 ·
Are you running an Alpha-N tune? Those additive and multiplicative look like they are not utilized.
 
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#9 ·
That is really strange then, the engine is always doing some trim adjustment, even minor. It's like your O2 sensors aren't doing anything.
 
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#12 · (Edited)
Thanks for the suggestions so far everyone - just been under the car, fixed a few things and went for a test drive, the report:



The other thing that is way odd is that your precat O2 voltages are not fluctuating. They should flip every few seconds from low to high. Yours are sitting at 0.45. Like it's running in open loop. Which it shoudn't be at 79 C.
I checked, the bank 1 sensors were connected... to each other. Just as Sailor24 said - I'm not sure we can get much from the readings prior to this post.

Screeners of INPA don't really tell me much because they all look the same healthy unhealthy the trims usually show perfect. I did notice a couple of odd numbers first is your voltage. The second is the MAF reading bottom left of Analog 1 Total HLM. I have little faith in INPA because the scale for that is claimed KG/HR and the bar goes to 100. I have compared that number to my scanner I am pretty sure that is calc load as a percentage. Our cars use way more air than that even at idle. Just off the top of my head I think we use more than 700 kg/h at WOT, what good would a scale of 100 be? Actually I think it is way more than even 700 but don't remember and to lazy to do the math.

Anyway the point I am getting to is that number appears high it should be 18 -20 at idle. How old are your MAFs and have you done a road test for them? What were your results?
MAFs are about a couple of years old now, but this thing has barely turned a wheel in the last year because of all the fun I've had with the crappy shop I asked to diagnose a coolant leak with the motor. I'll attempt to do a MAF test at some point.

I checked the fuel pressure regulator vacuum line - it seems connected OK at both ends.

The result of reconnecting the bank 1 lambda sensors is the car definitely runs worse, at a constant throttle, (under ~2k RPM) it surges. It's not so noticeable above that.

Got some new codes and analog values, interestingly I get lambda regulation codes for both banks now, and the car still thinks the lambda sensor on bank 1 is bad - I wonder if it's been killed by the bad fueling caused by it being disconnected for the couple of hundred miles I've done when testing.

First up, codes (I reset these before the test drive):



Analog values:


Video of analog values - note how bank one seems to report OK then drops to zero @ 55 seconds?


Other observations, bank 1 smells really rich.
 
#10 ·
Screeners of INPA don't really tell me much because they all look the same healthy unhealthy the trims usually show perfect. I did notice a couple of odd numbers first is your voltage. The second is the MAF reading bottom left of Analog 1 Total HLM. I have little faith in INPA because the scale for that is claimed KG/HR and the bar goes to 100. I have compared that number to my scanner I am pretty sure that is calc load as a percentage. Our cars use way more air than that even at idle. Just off the top of my head I think we use more than 700 kg/h at WOT, what good would a scale of 100 be? Actually I think it is way more than even 700 but don't remember and to lazy to do the math.

Anyway the point I am getting to is that number appears high it should be 18 -20 at idle. How old are your MAFs and have you done a road test for them? What were your results?
 
#13 ·
That is significant. So bank 1 were wrong, plugged together? Was the first set of screeners with them plugged wrong? That would explain some of what we see. Unplug your MAFs and see if there is a difference. But one bank rich the other lean very strange will need to think on this one. Exac tly what work did these clowns do?
 
#15 ·
That's correct - the first set of screenshots and video is with the lambda sensors connected incorrectly.

The shop installed a second hand motor, including putting a new timing chain on the new motor. All the intake components were moved from the old to the new - unfortunately the scope here is massive. It's worth noting that the old motor ran great apart from a coolant leak internally, so the components should be fundamentally good.

It does seem to report as if it's cold. The lack of fuel trim adjustment is just odd to me with MAFs plugged in.
I'm pretty confused about it - I don't think I've ever had the car run this badly after any of my previous rebuild attempts :p


I'll try running with the MAFs disconnected - any thoughts about the lambda voltage dropping to zero on bank 1? Could that be a dead sensor?
 
#14 ·
It does seem to report as if it's cold. The lack of fuel trim adjustment is just odd to me with MAFs plugged in.
 
#16 ·
Your O2 sensor wires could also be swapped left-right. That could explain why one bank is at positive lambda integrator limit and the other at negative lambda integrator limit, they are being corrected in the wrong direction if the O2 connections are swapped from one side to the other. This has been found on a few vehicles after transmission / engine out type jobs.
 
#17 · (Edited)
Just ran without the MAFs - no noticeable improvement.



Thanks, this is an interesting idea! I'm trying to remember what the wiring looks like from the last time I put the motor back in - is there a definitive way to tell which side goes where?

edit: I'm thinking the lengths are different, right? So makes it pretty obvious which side goes where.
 
#18 · (Edited)
I have looked through WDS and can't find any wire colours on the diagrams for the 4 oxygen sensors which is a shame as that could have made life easier. The cables (black sleeved) come down the firewall and then two of them cross over the transmission cross-member in metal clips. They are then held against the floor by the heatshield parts and plastic under trays (from memory).

If they are wrong then they are wrong in pairs as the pre and post cat values do follow each other for each bank.

I'm 90% sure the lambda integrator values in INPA represent short term fuel trims and a value over 1.00 is increasing fuel from the base value and under 1.00 is reducing fuel. I have watched your video several times and it does look like the changes to the lambda regulator on bank one have greatest affect on the sensors that the DME thinks are bank 2 and vice-versa. I can't think of any other fault that could cause such an effect.

Edit: It was assumed the lengths wouldn't allow this error but it has occurred on at least one other vehicle on this board. It took a long time to diagnose because it didn't look possible. I've tried to find the thread to take a look at the screenshots posted there but haven't found it yet!
 
#20 ·
Sorry, should have thought of this earlier. You say that the bank 1 sensors were wired to each other, was the connection you corrected under the right hand side of the car (UK driver's side). That would confirm that the connections were the ones the DME considers to be bank 1 and therefore they aren't swapped from one side to the other. If it was the left hand pair that were wired together then they are in the wrong place.
 
#21 ·
It was the left and side of the car (UK passenger) that were wired together. I've just realised I'm referring to the banks the wrong way round up til now in this thread - I thought bank one was on the left (from the driver's POV).

Based on that, it's the bank 2 sensors that were connected together, yet the codes thrown were for bank 1 which supports the idea the wiring is round the wrong way.
 
#23 · (Edited)
Looks like the wires were the wrong way round - just corrected it and went for a drive.

For reference, it's pretty obvious which way the wires go round, as the bank 1 wires cross over the gearbox support so are that much longer, and attach neatly into the right most bracket as sort of shown here:


These are the codes after this run:



Analog values 3-11s:

^ bank 1 integrator is really high, with low lambda voltage, integrator 2 is low and high lambda voltage.. edit: these are the same values as before the sensor wires were swapped?!

This time I had the MAFs connected, and had loads more power than the last time I was out with the lambda wires crossed. It's still surging on a constant throttle at low RPM, but less than before. Nice to have something that feels close to full power again, but there is still a problem in there somewhere.
 
#24 ·
Give it some time. When the DME gets as confused as it must be it will take some miles to sort out the trims. I am again shocked that this mistake is made. It is absolutely so clear which wires go to which side and you would really have to work at it to do it wrong. It is one of those mistakes I could not perceive as being possible. Seems idiot proof, which just goes to show everything gets improved, must be building better idiots everyday. I take it you will not be returning to that shop?
 
#25 · (Edited)
To update, is looks like there is a small coolant leak under the plenum - each time I jack the car up I see a few spots of coolant below the bell housing. I've had a leak in this location before and it's triggered the knock sensor (I guess it might be the metal changing coolant, or the water just interferes with the sensor) which might explain the current knock code.

I take it you will not be returning to that shop?
It's so disappointing - I paid a huge premium for a shop that actually builds race cars on a day to day basis to look at this, on a recommendation, and they've really done an awful job in all regards. They offered to fix the huge oil leak they caused too which I rejected (having found lose bolts in the plenum, spare bolts in the undertray) - I don't want them touching the thing again, I'll just take some money back instead.
 
#26 ·
I would replace the front O2 sensors, especially bank1. Is the coolant seeping from the thermostat o-rings or the heat exchanger?

You might want to also remove the knock sensor(s) and make sure they are clean as well as the seating surface.
 
#27 ·
I would replace the front O2 sensors, especially bank1. Is the coolant seeping from the thermostat o-rings or the heat exchanger?
You might want to also remove the knock sensor(s) and make sure they are clean as well as the seating surface.
OP

When you do the pipes during a tstat change, any ripped O ring will cause a small leak, It ends up at the back of the plenum. So check the tstat O ring but also the o rings on the pipes. The small pipe O ring is most prone to leaking. I don't know of any way of checking other than pulling the pipes, so make sure you have spare O rings on hand (2 different sizes for the 2 different sized pipes).

Regards,
Jerry
 
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#32 ·
Do you have access to a smoke tester or make your own? For bank 1, #17 plastic elbow can be suspect. Injector seals are another are that can be problematic. If the leak is so huge, you would think it would idle pretty poorly.
 
#33 · (Edited)
I've been thinking about this some more - the lambda values are reversed on each bank vs the voltage which suggests the wiring is the wrong way round, however I already went in there any made it fit correctly.

... or did I.

I'm wondering if it wasn't that the wires were round the wrong way, but the loom has been routed along the wrong side of the gearbox, making the longer length of wiring cross over to the wrong side but look right. Currently the wiring is coming down the left hand side of the gearbox, bank 2 side.

Just checked TIS and the only image I can find shows the wiring coming down the right hand side of the 'box (eg, the bank 1 side, from the driver's POV):



I'm going to try reversing the wiring back over tonight and see if the lambda situation improves.



Every time I'm troubleshooting a potential leak on this car I wish I had a smoke tester!
 
#35 ·
Hi. You initially found the bank 1 codes (from pre and post sensors joined in error) originally came from the left hand connections, which was the wrong side. Just as a simple check that they are now the correct way around I would temporarily unplug the sensors on one side, read the codes and see which bank has codes for the two unplugged sensors (or just look at the analogue values screen to see which have no output). You probably won't even need to start the engine for it to report heater codes. That will give you an absolute certain diagnosis of the connections.
 
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