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12-19-2021, 01:17 PM | #1 |
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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!
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12-22-2021, 06:32 PM | #2 |
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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.
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12-22-2021, 07:51 PM | #3 |
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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. |
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12-22-2021, 08:44 PM | #4 | |
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12-23-2021, 06:29 AM | #5 |
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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. |
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12-24-2021, 11:50 AM | #6 |
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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
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12-27-2021, 01:50 PM | #8 |
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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?
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12-27-2021, 08:31 PM | #9 |
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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? |
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12-27-2021, 11:38 PM | #10 | |
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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.
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12-28-2021, 03:10 AM | #11 | ||
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12-28-2021, 12:46 PM | #12 | |||
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12-28-2021, 12:51 PM | #13 | ||||
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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. |
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12-28-2021, 01:01 PM | #14 | |||||
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01-02-2022, 12:18 AM | #15 |
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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! |
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01-02-2022, 12:36 AM | #16 | |
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01-02-2022, 10:04 AM | #17 |
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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.
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01-02-2022, 10:13 AM | #18 |
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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.
Last edited by munstro; 01-02-2022 at 10:37 AM.. Reason: Clarity |
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01-02-2022, 01:44 PM | #19 | |
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01-02-2022, 07:49 PM | #20 | ||
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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. |
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01-02-2022, 08:10 PM | #21 | |||
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01-08-2022, 05:12 PM | #22 |
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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
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