27B0 will not go away!!!

[Scrippy]

Hey guys,

I need a little help with 27B0 "secondary airflow low Bank 1". I have been battling this for 2 months now. So far I have replaced the following parts cleared codes and it seems to come back every 3rd or 4th cold start. No other codes or operational issues, just smelly exhaust. Air pump has strong suction at cold start. Can the pump be turned on with INPA?

1-Replaced both air valves w/gaskets on back of engine.
*Old valves were good still and engine block ports clear of obstructions when scoped.
2-Replaced the Y-hose from pump to valves.
*No cracks or leaks on old hose.
3-All (4) O2 sensors.

Could this just be an exhaust leak at the header flange just before O2's? I ordered new donut gaskets but they haven't arrived yet. Any relevant ideas are appreciated!

[Scrippy]

Well at this point I'm throwing parts at this. I just put on new exhaust donut gaskets at the flanges. I guess I'll see after a few cold starts if this is my fix.

[rcracin]

Donut gaskets is what I would've suggested.

If you’re running cats and have a smelly exhaust, then it’s a leak before the cats which is gonna be either donut gaskets or header gaskets.

If donut gaskets don’t solve it, remove the xpipe and stick a smoke machine into the header flange and see if you find a leak.

[Scrippy]

Originally Posted by rcracin

Donut gaskets is what I would've suggested.

If you're running cats and have a smelly exhaust, then it's a leak before the cats which is gonna be either donut gaskets or header gaskets.

If donut gaskets don't solve it, remove the xpipe and stick a smoke machine into the header flange and see if you find a leak.

Awesome, thanx for the idea! Stupid question will forcing air up the header back into the motor have any negative effect? I could hook a shop vac up to the header as well and run smoke by the manifold to engine matting area as well to see if it dives in.

[rcracin]

I wouldn't do that. It would be too much pressure and who know what dirt and debris would travel up and into the motor.

The smoke machine operates at very low psi. I once paid a shop $100 to do it but I've since bought my own machine off ebay.

[Scrippy]

Jesus Christ this will not go away! I replaced both donut gaskets and hardware. All torqued down and the god damn code came back on the 4th cold start

[rcracin]

you still smelling fumes? You running cats? Maybe the bank 1 cat is clogged?

[Scrippy]

Originally Posted by rcracin

you still smelling fumes? You running cats? Maybe the bank 1 cat is clogged?

I am smelling fumes at the tail pipe. My car is 100% stock, so yes to cats and soick mid pipe. It drives fine and has no hesitation. Next is going to be the intake hose for the pump with sensor. I understand this may not be the proper test but I am getting equal exhaust air flow at the pipes. I agree this may be my cat at this point. When I run the lambda analog area in INPA the (4) O2's are giving the same values relative to before and after the cat for both banks give or take .8. Can a smog or exhaust shop determine this definitively ya think?

[BPMSport]

Before you replace that expensive pipe, I would first check it for logical metering of air on cold start. Iirc, it should be seeing about 30-45kg/h while the pump is running.

sls_obdh_mdf_max_intg_norm (after roughly 30s)<K_SLS_OBDH_MDF_MIN_DEF and
sls_obdh_lam_asv_intg_norm < k_SLS_OBDH_MDF_2_MAG or
sls_obdh_lam_asv_intg_norm < k_SLS_OBDH_ASV_LI_OPE and K_SLS_OBDH_MDF_MIN_DEF>K_SLS_OBDH_MDF_MAX_DEF
Terminal condition: Engine running
Voltage condition:
Battery voltage > 10.8 V (k_sls_obd_ub_min)

According to the conditions for fault memory above, it must be a disparity between the Mini HFM and the oxygen sensors. Have you tried switching the two primary sensors to see if you then trigger 27B1?

[Scrippy]

Originally Posted by BPMSport

Before you replace that expensive pipe, I would first check it for logical metering of air on cold start. Iirc, it should be seeing about 30-45kg/h while the pump is running.

sls_obdh_mdf_max_intg_norm (after roughly 30s)<K_SLS_OBDH_MDF_MIN_DEF and
sls_obdh_lam_asv_intg_norm < k_SLS_OBDH_MDF_2_MAG or
sls_obdh_lam_asv_intg_norm < k_SLS_OBDH_ASV_LI_OPE and K_SLS_OBDH_MDF_MIN_DEF>K_SLS_OBDH_MDF_MAX_DEF
Terminal condition: Engine running
Voltage condition:
Battery voltage > 10.8 V (k_sls_obd_ub_min)

According to the conditions for fault memory above, it must be a disparity between the Mini HFM and the oxygen sensors. Have you tried switching the two primary sensors to see if you then trigger 27B1?

I cannot get anywhere with this lol. Here my already installed new parts list based off 27B0
1-Both EGR Valves.
2-Y-hose for aforementioned.
3-All (4) O2's
4-New donut gaskets

Lol the last two things for me to replace are the pump and that intake hose with sensor. After each step of parts above I still get 27B0. Only 27B0 persists.

[BPMSport]

Originally Posted by Scrippy

I cannot get anywhere with this lol. Here my already installed new parts list based off 27B0
1-Both EGR Valves.
2-Y-hose for aforementioned.
3-All (4) O2's
4-New donut gaskets

Lol the last two things for me to replace are the pump and that intake hose with sensor. After each step of parts above I still get 27B0. Only 27B0 persists.

Your response makes it very clear why you're not getting anywhere.. Try reading my post again..

[Scrippy]

Originally Posted by BPMSport

Your response makes it very clear why you're not getting anywhere.. Try reading my post again..

Are you referring to the pre cat O2's? I've replaced them so I'm not sure why I would swap bank 1&2 now. I did read your post and I am not comprehending the middle section at all. I don't know what a mini HFM is. I assume it's the air sensor on the vacuum feed pipe. Other than that I am unaware of individual air flow monitoring for banks 1&2 prior to the O2's.

[BPMSport]

Originally Posted by Scrippy

Are you referring to the pre cat O2's? I've replaced them so I'm not sure why I would swap bank 1&2 now. I did read your post and I am not comprehending the middle section at all. I don't know what a mini HFM is. I assume it's the air sensor on the vacuum feed pipe. Other than that I am unaware of individual air flow monitoring for banks 1&2 prior to the O2's.

Yes, that's what the Mini HFM is.

There is a reason to switch as a double check or I wouldn't suggest it. I can't count on my fingers and toes the number of bad oxygen sensors we've received, even brand new.

[Scrippy]

Originally Posted by BPMSport

Yes, that's what the Mini HFM is.

There is a reason to switch as a double check or I wouldn't suggest it. But if you don't want to, it's up to you

Gotcha yeah I really don't want to swap them again. I replaced all 4 O2's with new and I doubt that I got a bad new one and happened to place it on the same bank that hates my existence. I already ordered the vacuum feed pipe a few days back so I'll see.

[sumtingwong]

I have the same problem as well and have been throwing parts at it as I try to narrow it down, but mines on bank 2 (27B1). Going to try what Mike at BPMSPORT suggested and swap the Pre-Cat O2 sensors and see if it switches despite I have also swapped all 4 o2 sensors with new ones.

My last resort is to swap my cats on my other M3 and see if my cats are just bad.

Hope you'll be able to resolve this Scrippy and hope to see an update on here!

[Scrippy]

Originally Posted by sumtingwong

I have the same problem as well and have been throwing parts at it as I try to narrow it down, but mines on bank 2 (27B1). Going to try what Mike at BPMSPORT suggested and swap the Pre-Cat O2 sensors and see if it switches despite I have also swapped all 4 o2 sensors with new ones.

My last resort is to swap my cats on my other M3 and see if my cats are just bad.

Hope you'll be able to resolve this Scrippy and hope to see an update on here!

Ya Mike knows best for sure and reluctantly I f'ng swapped my O2's AGAIN and still I keep getting 27B0. Never 27B1 Literally I've replaced the whole system minus the pump and intake hose. My intake hose is still shipping but I should have it within the next 3 days. I'm hoping the disparity between O2 readings before and after is a wonky intake sensor. I would think I'd have both banks erroring or a intake sensor plausibility error if this was the case but the money is already spent so here I go. I'll report back after if I experience positive effects after multiple cold starts. Btw none of my original parts were bad as I saw after removal. The egr valves had maybe 1mm of buildup but still only allowed air flow one way only. The Y-Hose had no cracks or leaks. 4 new O2's yielded the same error post install. Both new donut header collector gaskets yielded the same error post install. My neighbor has a video scope and I scoped the passages on the heads and they had only a very fine buildup, nothing obstructive at all. After any parts were installed I cleared errors and lambda adaptations with INPA but here I am still lol. Maybe it's my bank 1 cat? If you read this and have any ideas please do share!

[munstro]

For me it was this sequence. Replace O2 sensor, upload most current software. Replace O2 sensor again, then new DME. Engine wiring harness, then new factory x pipe. Problem fixed thankfully mostly under warranty. For a car not under warranty I’m thinking a tune and removing the cats is your easiest way out of this problem.

[munstro]

After my DME got replaced it started throwing an additional code for both cats. We hoped the wiring harness would resolve the issue, and the cats were scoped and determined to be ok. After the wiring harness was replaced the code came back, this time thankfully only for the cats. They were then replaced and the problem is resolved. Given the mileage on your car I would think trying a lower mileage used OEM x pipe might be another place to go without the mess of the wiring harness. I’ve outlined this whole mess before in these threads but the opinion is not popular but in retrospect it was successful for me and worth it for a low mileage car. Also if you go way back you’ll find another guy who had a rare newer at the time m3 had the same issue that was resolved in the exact same manner as mine.

[Scrippy]

Originally Posted by munstro

For me it was this sequence. Replace O2 sensor, upload most current software. Replace O2 sensor again, then new DME. Engine wiring harness, then new factory x pipe. Problem fixed thankfully mostly under warranty. For a car not under warranty I’m thinking a tune and removing the cats is your easiest way out of this problem.

I'd love to remove the cats and tune out the secondary air system but California smog is a nightmare.

[BPMSport]

Originally Posted by Scrippy

I'd love to remove the cats and tune out the secondary air system but California smog is a nightmare.

You can always purchase a remote diagnostic session and we can look at the flow through the HFM and a number of other things to try and track down the issue.

If you leave it for a month without clearing, do any other faults come up other than 27B0?

It's suggested not to keep clearing it as looking at the logistics counter and freeze frame of every entry provides useful information as to the circumstances under which the fault was triggered.

At this point I would have an expert like us take a look, or take it to a shop. Throwing parts at it doesn't make sense.

[Scrippy]

Originally Posted by BPMSport

You can always purchase a remote diagnostic session and we can look at the flow through the HFM and a number of other things to try and track down the issue.

If you leave it for a month without clearing, do any other faults come up other than 27B0?

It's suggested not to keep clearing it as looking at the logistics counter and freeze frame of every entry provides useful information as to the circumstances under which the fault was triggered.

At this point I would have an expert like us take a look, or take it to a shop. Throwing parts at it doesn't make sense.

I just might have to do that. To answer your question no this is the only error I find every time. I have screen shots of the errors going back to October as the DME lists them in INPA. I already ordered the hose and it's supposed to arrive Monday. I will put it in and triple check the wiring harness connections while the plenum is off. If the error persists I will reach out you guys via your website Mike. I'll schedule a remote session and start there. I suspect there are bigger problems for me leading to this constant error.

[Scrippy]

So I replaced the intake hose and sensor to the secondary air pump part#11727838504. The same error came up along with another which I attribute to leaving my iPhone plugged into the snap in adapter and it drawling power charging the phone. Here is the error from INPA and its calling out bank 1 valve being stuck. I replaced both valves and hose, so Im tripping out here. I scoped the ports when I replaced and both were clear. Can I turn on the secondary air pump with INPA? I would like to do this to check the air flow if possible. Here are the translated errors...lf I was to remove the outgoing Y-hose from the pump and start the car wouldn't I get back flow from the engine exhaust if the valve was stuck open?

27B0 Secondary air system throughput bank 1

P0491 Air System (Bank 1) - Low flow rate

Error rate: 1
Logistics counter: 40

Mileage 376688 km
Ratio of secondary air volume from HFM to LAM 1.18 -
OBD-Secondary air system standard deviation integral maximum 0.00 kg / h
OBD-Secondary air system standard deviation intgral min 10.25 kg / h
Secondary air system Air mass ratio Bank1 / Bank2 via lambda signal 0.46 -

Shut-off valve 1 is stuck
Test conditions met

Errorcode: 27 B0 E4 04 91 01 28 B7 EE 04 B9 00 00 05 01 01
D6
================================================== ==================================

279D Power Management Battery quiscent current violation

Error rate: 2
Logistics counter: 40

1. Environmental principle
Mileage 376,480 km
Time with quiescent current 80-200 mA 552.53 min
Time with quiescent current 200-1000 mA 14.93 min
Time with quiescent current> 1000 mA 0.00 min
Distance to starting ability limit 26.16 -

2. Environment phrase
Mileage 376688 km
Time with quiescent current 80-200 mA 522.67 min
Time with quiescent current 200-1000 mA 0.00 min
Time with quiescent current> 1000 mA 0.00 min
Margin for startability limit 29.56 -

Quiescent current higher than allowed
Test conditions met

Errorcode: 27 9D 48 00 00 02 28 B7 D4 00 25 00 01 00 00 21
7C B7 EE 00 23 00 00 00 25 D5