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Thread: Secondary Air Injection System Insufficient Flow P0491 & 2

  1. #1
    Join Date
    Jan 2018
    Location
    Florida
    Posts
    28
    My Cars
    2003 745 Li

    Secondary Air Injection System Insufficient Flow P0491 & 2

    Have been going around with the mechanic with this for several months. According to him this system is only used at "cold start" and has no effect on the performance. It injects air into the exhaust manifolds for more complete fuel burn. It normally shuts down after a few seconds when the engine warms. He has worked on this trying to clean the ports without having to remove the heads ($3k-$4K). I asked him if he could just delete the system from the computer software as the system has no effect on performance. His response was he can see the programming code but, not being a programmer has no idea where in the hundreds of thousands of lines of code the system exists. He said he will continue to look into it. He also suggested there is now a software tune available for the E65. For about $500 he sends off a module (?) to be "flashed". The result being a few more HP, MPG and the Secondary Air Injection System is deleted from the software ergo the "Check Engine" light goes off so I will know when another problem surfaces.

    If anyone has any thoughts, knowledge, experience, etc. about this, it would be greatly appreciated.

    Thanks, Friz

  2. #2
    Join Date
    Jun 2017
    Location
    Denver, CO
    Posts
    264
    My Cars
    325xi; 740i
    E46 can have the same thing done. With ours we can run the EU3 tune which removed SAP (secondary air pump) and disables the post cat oxygen sensors preventing cat inefficiency codes. $500 sounds about right for a tune, the active autowerks for the E46 is about $450. What I think is kind of funny is officially licensed mechanics cant knowingly remove or disable any emissions systems but nobody checks lol. ( I used to be a dealership technician)

    Just some two cents.
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  3. #3
    Join Date
    Jan 2018
    Location
    Florida
    Posts
    28
    My Cars
    2003 745 Li
    Primo! So it sounds as if this tune now actually exists for the E65 as per the mech. I won't do anything to put this man in jeopardy. Thanks for the heads up.

  4. #4
    Join Date
    Jan 2018
    Location
    Florida
    Posts
    28
    My Cars
    2003 745 Li

    Secondary Air Injection System Insufficient Flow P0491 & 2

    Have been going around with the mechanic with this for several months. According to him this system is only used at "cold start" and has no effect on the performance. It injects air into the exhaust manifolds for more complete fuel burn. It normally shuts down after a few seconds when the engine warms. He has worked on this trying to clean the ports without having to remove the heads ($3k-$4K). I asked him if he could just delete the system from the computer software as the system has no effect on performance. His response was he can see the programming code but, not being a programmer has no idea where in the hundreds of thousands of lines of code the system exists. He said he will continue to look into it. He also suggested there is now a software tune available for the E65. For about $500 he sends off a module (?) to be "flashed". The result being a few more HP, MPG and the Secondary Air Injection System is deleted from the software ergo the "Check Engine" light goes off so I will know when another problem surfaces.

    If anyone has any thoughts, knowledge, experience, etc. about this, it would be greatly appreciated.

    Thanks, Friz

  5. #5
    Join Date
    Jan 2016
    Location
    Ca
    Posts
    6,981
    My Cars
    2001 525it
    He is right, the system only works on the first start of the day, sure it could work on a restart the same day but the engine would have to get cold enough to allow the system to operate. Since extra fuel is used on the first start up, ambient air is pumped into the exhaust ports to dilute the rich mixture before it reaches the pre cat ox sensors. The system is monitored the the pre cat oxygen sensors. The pump comes on the valves open and air is pumped in. Carboned up passage ways won't flow enough. The main passage way certainly could be clogged but the very small passage ways in the exhaust ports are probably the real culprit. It could be programmed out. I know people have done it on e39 m5's. The engine computer would have to be altered

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