[SR77]

Hello,

I have a 2008 328i Sedan with a N51 and Secondary Air Injection. Can anyone tell me where the Secondary Air Mass Sensor is located?

I have tried searching here and google but can not find it. Does this year N51 have one, or it is only early years of the N51? Or is it built into the pump or something? I have seen the Bentley Diagrams on here that show it on the inlet air filter hose, but no sure if this was just early N51s.

I keep getting an SES dash light for "Insufficient Flow Bank 1 & 2" and I am trying to learn all the parts of the Secondary Air Injection System and how it works so I can try to narrow down what might be wrong. Pump is working fine and have a new Value so it is not either of those.

Thanks for the Help!

[gbalthrop]

I don't have an N51, but here are screenprints from Bentley Manual, showing HOW system works & components.
George

[SR77]

Hey George,

Thanks for replying. Yes that is the manual diagram I was referring to that I am confused on.

The second image represents my pump, and is says B2606 Mini Mass Air Flow Sensor (If Equipped)? Not all N51s had one?

When I am looking at my intake hose which points to down near the filter, I dont see a sensor on the hose or any harness connection that a sensor would plug into. Also when I try to look up a new sensor on sites like FCP/ECS for my model year, it says it cannot find a Mini Mass Air Flow Sensor and their intake hose shows it just has a filter on the end.

Did some years N51 not come with a Secondary Air Mass Flow Sensor? How does the system monitor the air flow without one?

I am trying figure out what is causing my SES dash light for Insufficient Airflow Banks 1 & 2, and my system does seem to match the diagrams out there like above that state an Air Mass Meter is on the intake hose by the filter.

Thanks again

[Cal122]

FWIW I don't have the mini-mass air flow sensor on my N51 either, it's just the hose with the filter on the end and then one electrical connection to the pump. (Thanks George for the share!).

BavAuto had an article on diagnosing the Secondary Air Pump system on the E46s, but this setup is common across different BMW models/engines. In case helpful, check out pages 6&7 https://www.e46fanatics.com/attachme...ms-pdf.435680/

Hope you're able to sort out the issue. The potential for carbon to build-up up and clog the air passageways on the engine is something that worries me on my N51 since there isn't anything published on how I can prevent this from happening. If you search for BMW secondary air pump/carbon build up, there are some forum posts with things people tried in place of having to send to send the engine out to remove the carbon.

[SR77]

Cal, thanks for posting.

Is the Mass Air Meter in a difference location for some N51 years, like in the pump itself or did it just not have one at all. If this is true, how does the system Monitor the air flow?

Yes, that is my next worry to. Since my pump and Check Value are new, and if there is no Air Mass meter monitor in the flow, then I am worried about a blockage. That was going to be my next thread, because I don't have it in my budget for this car to be pulling the head to be cleaned. I have searched some on a DIY cleaning method but have not found much that people say worked or fixed their issue. I am running out of ideas on how to fix this SES light and the fact that it says both bank 1 & 2 is making it more difficult.

[Cal122]

I wasn't able to locate one on my car or in any of the part diagrams, so assuming it either doesn't have one or it's built into the pump.

From the Bentley pictures, I was able to find that sensor, but it looks like it only applies to different engine models.

https://www.realoem.com/bmw/enUS/sho...56#11721438814

[SR77]

Thanks Cal,

For a system that seems like it should be straight forward, this is a head scratcher.

I will keep at it!