Bank 1 system running lean code

[M3 Number 86]

Has anyone dealt with this? Searching just shows n54/55 or s55 related posts.

I've replaced precat sensors and they've come back. Replaced donuts on header to xpipe connections. Reflashed to stock. There are other codes but I'm IGNORING those assuming it's a computer trip due to the main culprit (misfiring). I've replaced plugs and don't feel or see/hear misfiring. It could be fuel delivery clogging but that wouldn't only be on one bank either right?

I can check throttle bodies for leaks but would that throw a code for only one side?

I'm going to swap sensors bank 1 and 2 to see if the code follows. From there if the code doesn't follow I'll have a look at the header connection up top. Possibly a leak there but can't really tell unless pulled.

This is driving me crazy. The threads on here all seem to end without a solution reported.

[Makaveli7]

Looking at all these codes together, imo, it cannot be related to injectors/coils/plugs as it is hitting all 8 cylinders in 1 go. I would say this looks like a sensor that feeds information to all other sensors - Of course keep in mind that there are many answers to why would these errors all come up.

There should be another code to complement the 27BA which would also help, not sure if INPA or ISta would be a better way to read those codes - Click here to see the technical advice on it

https://www.m3post.com/forums/showpo...5&postcount=68

If I was in you shoes I would do the following to try to get my head focused more:

1- Check the oxygen sensors that you installed and the old ones- check the connection lines and ensure they are properly installed.

https://www.newtis.info/tisv2/a/en/e...sensor/OenHnRX

https://www.newtis.info/tisv2/a/en/e...sensor/Og21pSE

2- Check the fuel pressure sensor - This is the sensor on the left side in the engine bay, I have faced many e92 m3s with faulty ones which gave similar issues - I would start with the connections and move down to the actual sensor (cleaning and retrying).

https://www.newtis.info/tisv2/a/en/e...nes/1VnXgx7DaX

3- Check the MAP sensor - with the same mentality that it might be a connection issue to start with. I am leaning towards saying it might be this as It looks more like air volume issue, but not sure if it should have thrown a separate error on the sensor if it was faulty (Also try checking if the plenum is properly installed as it might also impact this, but not as severe as a map sensor)

http://www.realoem.com/bmw/enUS/show...diagId=13_1241

https://www.newtis.info/tisv2/a/en/e...l-unit/ObhgCEq

I think if you drill down that road and it is a wiring issue, it would get resolved as you would have went to the bottom of the engine.

Let us know how it goes and if you come up with any new finding.

This might end up to be a simple fix, as simple as when i got a solenoid error on bank 1 to figure out after 10 days that the camshaft sensors line on bank 1 were swapped

[M3 Number 86]

Originally Posted by Makaveli7

Looking at all these codes together, imo, it cannot be related to injectors/coils/plugs as it is hitting all 8 cylinders in 1 go. I would say this looks like a sensor that feeds information to all other sensors - Of course keep in mind that there are many answers to why would these errors all come up.

There should be another code to complement the 27BA which would also help, not sure if INPA or ISta would be a better way to read those codes - Click here to see the technical advice on it

https://www.m3post.com/forums/showpo...8;postcount=68

If I was in you shoes I would do the following to try to get my head focused more:

1- Check the oxygen sensors that you installed and the old ones- check the connection lines and ensure they are properly installed.

https://www.newtis.info/tisv2/a/en/e...sensor/OenHnRX

https://www.newtis.info/tisv2/a/en/e...sensor/Og21pSE

2- Check the fuel pressure sensor - This is the sensor on the left side in the engine bay, I have faced many e92 m3s with faulty ones which gave similar issues - I would start with the connections and move down to the actual sensor (cleaning and retrying).

https://www.newtis.info/tisv2/a/en/e...nes/1VnXgx7DaX

3- Check the MAP sensor - with the same mentality that it might be a connection issue to start with. I am leaning towards saying it might be this as It looks more like air volume issue, but not sure if it should have thrown a separate error on the sensor if it was faulty (Also try checking if the plenum is properly installed as it might also impact this, but not as severe as a map sensor)

http://www.realoem.com/bmw/enUS/show...diagId=13_1241

https://www.newtis.info/tisv2/a/en/e...l-unit/ObhgCEq

I think if you drill down that road and it is a wiring issue, it would get resolved as you would have went to the bottom of the engine.

Let us know how it goes and if you come up with any new finding.

This might end up to be a simple fix, as simple as when i got a solenoid error on bank 1 to figure out after 10 days that the camshaft sensors line on bank 1 were swapped

Thanks! I'll have a look. I also installed a smaller battery (and coded properly) but have a lot of power resourcing it. I wonder if it's either having trouble, or maybe lost it's coding while we did some reflashes although I don't think it would have changed.

[Makaveli7]

Originally Posted by M3 Number 86

Thanks! I'll have a look. I also installed a smaller battery (and coded properly) but have a lot of power resourcing it. I wonder if it's either having trouble, or maybe lost it's coding while we did some reflashes although I don't think it would have changed.

I really doubt the battery would cause this - My understanding from registering a new battery is that the alternator, over the age of the battery with the help of the IBS cable, would increase the charging output to compensate for the loss of power from the battery, hence, registering the new battery with a new lower amps, would tell the alternator to provide different charging power. However, theoretically speaking, the car should act normally, unless the battery is unable to provide enough power for the car to run its sensors properly. While you are at it, id suggest you actually check the cables, especially the IBS cable if you are doubting that it started after you have touched the battery.

[Richbot]

https://www.m3post.com/forums/showthread.php?t=836709

IACV? It's used in the fuel/timing maps IIRC?

[Makaveli7]

Originally Posted by Richbot

https://www.m3post.com/forums/showthread.php?t=836709

IACV? It's used in the fuel/timing maps IIRC?

Very possible! totally missed that - ICV and throttle actuators might also be the main issue behind this. imo one of the most expensive fix on this platform

[Richbot]

Just a thought I’m sure there’s a test procedure. Not sure if there are more codes he’s not showing us

[M3 Number 86]

Originally Posted by Richbot

Just a thought I’m sure there’s a test procedure. Not sure if there are more codes he’s not showing us

I've already replaced ICV and both throttle actuators a while ago. The thing is, it throws codes for them.

Cleared codes and ran the car and this time no lean condition code but now had misfire with cylinder deterioration.

Meh. Shop is gonna check after the new year. In the meantime I've removed my aero pieces to a more street friendly setup and will swap my kw clubsport a to jrz rs2. Hope it's an upgrade like I've been told by literally everyone I've asked lol

[M3 Number 86]

Originally Posted by Makaveli7

Very possible! totally missed that - ICV and throttle actuators might also be the main issue behind this. imo one of the most expensive fix on this platform

If you look at the link it threw an icv specific code.

All I know is I need to purchase another warranty now lol

[StripclubDJ]

Rod bearings

[Richbot]

nah man it's not the bearings that's a KW clubsport code but only with aero

[StripclubDJ]

Originally Posted by Richbot

nah man it's not the bearings that's a KW clubsport code but only with aero

Hmm I run aero and clubsports and the only code I throw is a U code in the body module.

U-a douchebag , I think the code is

[M3 Number 86]

Lol

[ItsGary]

Makaveli7

Apparently its common for the LPFS to go bad, I replaced mine since its a cheap part.

[M3 Number 86]

Small update: I was monitoring the o2 voltage (?) and the error side was reading something really low like 0.050-0.060. That doesn't seem right at all when the other side was reading around 0.600. It can't be that off at idle no? That sort of looks like there was a gaping hole somewhere or the exhaust piping was actually cut into two sections lol

What I've done so far is replace the fuel pressure sensor and it actually remedied my low idle issue. Car felt better on the initial drive but I was still hesitant to say success! I know it'll throw a code on the condition happening twice so I test drove it again. This time only the lean code on bank 1 popped up with no accompanying misfire codes. I'm wondering if that's a step in the right direction. I'll drive it again and see if I get any more codes.

And since it's only one bank I guess I can swap o2 sensors side to side, switch donut gasket side to side, possibly fuel injectors (could I data log to see in real time if it's faulty or will I only see how the car is reacting?) and go from there. Lastly I'll have to check the exhaust manifold at the head to see if there is a leak.

[M3 Number 86]

Update: swapped to oem xpipe to see if it would have a better clamp and low and behold fuel trims are 0% now. I'm going to shorten the o2 sensor bung so that the sensor is placed inside the pipes correctly. I'll report back once I do that. Here are fuel trims currently read. Stock xpipe with epic tune to rule out if it was the tune or not.

[M3 Number 86]

Update: swapped back to my catless xpipe. I modified the front bungs to sit shallow like the oem xpipe so that it can read proper airflow and car runs like a champ!

Have been driving the past couple of days and total fuel trims are at about -1.5%. Nothing wrong with that!

Three weeks of figuring things out and also learning how to read live data. Some cool videos on YouTube. One dude even has a quiz on there haha.